Lecture Notes for CS 428/528 Games and Virtual Environments

Syllabus

Reading Assignment

• Read Chapter 1.1 of the Rabin book, "A Brief History of Video Games"

What's This Course About?

• An introduction to games, genres, game design
• How to design and implement computer-based games
• How to develop collaborative virtual environments
• Graphics, networking, A/I, data structures, algorithms, I/O...

How can CS reduce the effort required to develop computer games?

What CS skills can we learn by studying game design and development?

What's This Course NOT About?

• Vocational/technical training for the game industry
• DirectX, Direct3D, or other platform-specific API's
• Modding or "level editing" of other people's games

Pirates

What is a Game

The main definitions we will consider are

an amusement or pastime

OK, but are movies and TV games? No.

a competitive activity involving skill, chance, or endurance...

having rules, etc.

Throwing all this together one gets something like:

A competitive or cooperative activity involving skill, chance, or endurance, whose primary goals are amusement, improvement, or both.

History of Video Games

Dr. J's Quick Take on the History of Computer Games

1952	First computer game (?) might have been Alexander Douglas' computer version of Tic-Tac-Toe (Noughts and Crosses). Although this is a graphics display, it might as well be ASCII-art
1958-59	Higinbotham builds Tennis for Two This is running on an analog computer. The screen is an oscilloscope. Hardware implementation. One instance built for public demonstration. This isn't Pong, but it seems valid to call it a predecessor. Proof that Sports Games came before Shooters.
1961-62	Russel builds Spacewar Software widely replicated as a "diagnostic tool". Inspired videogame entrepreneurs. Cloned into commercial existence in 1970's.
1960's	While spacewar was slowly propagating... games such as checkers considered by A/I pioneers. Punched card era also inspired trivial sim games (e.g. Hamurabi)
70's	pencil RPG's Textual games and ASCII art. Usually turn-based. On-line == modems: rare and institutional. The precursor to the FPS: Mazewar
late 70's	Arcade games. Pong, space invaders, Pac Man... Precursor 4k-64k personal computers often had lower fidelity graphics than the commercial arcades. Check out C64s.com
80's	early multi-user games. (low-res) turn based strategy Let us not forget awesome console franchise empires such as Nintendo and Sega. The Rabin book has sections on some of them. You may be nostalgically attached to one or more iconic figures such as Mario, or Sonic the Hedgehog. I am not sure that the Rabin book emphasizes enough the closed and controlled nature of console development, and what implications it has for the industry.
90's	FPS, RTS. From id software came the game Doom, which catapulted PC gaming to the fore, and spurred intense development of low-cost mass market 3D graphics hardware.
2K+'s	MMRPG, ...

Current Platforms

• Wii, Xbox360, PS3
• PC and Mac
• handheld and cellphone
• web

Game Development via "Evolution"

Requirements Analysis	The gamer has an idea, not found in current games Idea is explored, and a "vision" for a new game is realized.
Design	Game User Interface. File formats. Network communication protocols.
Implementation	Coding and Art. Ratio varies. Art is overwhelming coding in modern commercial games.
Testing	Hire gamers at $6/hour to test your game. Alpha and beta test.
Release	Release your game through a publisher and distributor, or via internet.
Maintenance	If you get this far, you are more successful than 98% of game efforts.

Actually, the waterfall model is "all wrong" for game development, which should probably follow a "natural evolution", meaning working prototypes start out with textual depictions of core game logic, proceed to simple graphics, and then evolve more powerful 3D and multi-user capabilities. Whether or not each individual game should evolve in this manner, there is another possible application of the metaphor.

Corollary Evolutionary Hypothesis: just as embryos, fetuses, and infants are claimed to go through the earlier stages of evolution of our species, our individual capability to write computer games might best be "grown" one game at a time by implementing each and every game and game genre that was previously done by our forefathers. When we can clone Wow, then we can talk about implementing Wow's successor.

Popular Game Genres and Mechanics

parlor games

computer versions of manual games can be very popular.

text adventures

textual games that require players to solve puzzles and mysteries

arcade

2D games of exploration or survival

first person shooters

3D real-time games of combat/survival

survival

run, or shoot, until you die. Examples: Space Invaders, Doom

escape

win by getting out

genocide

win by eliminating the opponent. Example: checkers

assassination

win by killing the enemy king. Example: chess, stratego.

collection

win by completing your collection of rare and exotic items (or deeds)

construction

build cool stuff

tycoon

win by amassing the most money

celebrity

win by amassing the most "fame"

megalomania

win by taking over the world, a la Napoleon / Alexander / supervillain

tactics

win a battle, by accomplishing specific military objectives

strategy

win a war, by defeating the enemy across multiple battles. Usually involves out-resourcing, out-logisticsing, or out-sciencing them. Examples: Civilization, Warcraft

exploration

win by finding or discovering something, or everything

role-playing

you don't win, you just enhance your character, get "xp" and gain "levels"

Learn Unicon by Means of Simple Classic Games (UG Chapters 1-6)

procedure main()
   write("Hello, amigo!")
end

   write("die roll: ", ?6)

   write("coin toss: ", ?["heads", "tails"])

every 1 to 3 do write("crazy")

	words := ["fish", "beagle", "minotaur", "tiger", "baseball"]
	word := ?words

	scramble := word
	every 1 to 99 do
		scramble[?*scramble] :=: scramble[?*scramble]

procedure main()
    words := ["fish", "beagle", "minotaur", "tiger", "baseball"]
    word := ?words
    scramble := word
    every 1 to 99 do
        scramble[?*scramble] :=: scramble[?*scramble]
    write("Unscramble: ", scramble)
    answer := read()
    if answer == word then
        write("correct!")
    else write("no, it was ", word)
end

Reading Assignment

• Read Rabin book Chapter 1.2
• Read Chapters 1-6 of Dr. J's Unicon Games book.
• Read Why Minecraft Matters

Game Competitions -- for what they're worth

• Queue ICPC Challenge - C, C++, Java, or Python
• Imagine Cup Game Design Competition - MS, MS, MS, or MS

Rabin Book, Chapter 1.2

Homework Assignment

Highlights of UG book Chapters 1-6, cont'd

Ascii Art:

	hangedperson := [
	"  o  ",
	"\\ | /",
	" \\|/ ",
	" /|\\ ",
	"/ | \\"
		]

    if misses = 5 then
	stop("you lose! The word was ", word)

    if find(letter, word) then
	every i := find(letter, word) do
	    blanks[i] := word[i]
    else misses := misses + 1

	w := open("hangman", "g", "size=400,400")
	DrawCircle(w, 300, 50, 25)
	DrawLine(w, 300,75, 300,150)

Chapter 3: Dice Games

	dice := [ ?6, ?6, ?6, ?6, ?6 ]
	write("The dice are: ",
		dice[1], dice[2], dice[3], dice[4], dice[5])

	write("Which dice values do you keep?")
	keep := read()

	# Reroll the dice
	every i := 1 to 5 do {
		if not find(dice[i], keep) then
			dice[i] := ?6
		else keep[find(dice[i], keep)] := ""
	}

	dice := sort(dice)

   if dice[1]=dice[2]=dice[3]=dice[4]=dice[5] then ...
   else if dice[1]=dice[2]=dice[3]=dice[4] then ...
   else if dice[1]=dice[2]=dice[3] then ...

Brief Summary of Rules of Yahtzee

More generally: I welcome input where the Game Book needs additional material, and when it is missing something, I welcome questions. But when you need some info like this, please use google and dig it up. Lecture 3

Mailbag

How do I declare "private" variables in Unicon classes?

Sorry, Unicon and many other dynamic languages use "bedroom door privacy", not "10-foot-walls-between-neighbor's-houses" privacy.

If someone enters "1 3 5 4 2" how do I get those into separate variables?

How about

L := []
"1 3 5 4 2" ? {
   while put(L, tab(many(&digits))) do
      tab(upto(&digits))
}

Mention of Pirate Resources Page

Rabin of the Day

Text Adventures and ASCII Art Games

Most computer games are simulations of some imaginative situation. The computer both (a) allows more detailed simulations than players can manage using pencil and paper, and (b) frees the player from the need for a referee or game master.

Text Adventures

The ORIGINAL text adventure Infocom games (Java applets) Hamlet adventure (original cia.icn) improved cia2.icn

Steve Jackson wrote an article on writing interactive fictions which may be of interest.

Lecture 4

Lecture notes from last week

Thank you, Lawrence! Note to future scribes: No need to repeat material explicitly given on my lecture notes, but fine to repeat section headings in order to provide context for your additions.

Scribe This week:

Daniel Norris.

Comments on Homeworks

• I expect sophistication of solutions to vary widely
• format your code for printable hard copy
• break long lines; maximum line length is 80
• indent 3-4 spaces per syntax level
• Bugs to Avoid
  • no paper copy; paper copy with unreadably small font
  • turning in something I can't run; particularly:
  • turning in with syntax error
  • not writing enough output for user to tell where they are and what they are doing, user getting "lost"
  • defining/applying the rules carefully
  • not checking input carefully
  • making it unclear how to quit; quitting awkwardly
  • if answer == 'y' (no character literals in this language)
  • not using +:=, -:=
  • not using case str of { "this": { ... } "that": { ... } }
  • not using x < y < z
  • if find(2&3&4&5, !dice) ...
  • using $include when you should link

Reading Assignments

• Sswink's blog post on "Game Feel"
• Chapters 7-9 of the Unicon Games Book
• Rabin 2.1: Understanding Fun

Text Adventures, cont'd

Anatomy of a Text Adventure

Now, let's generalize: what if the goal were a text adventure program that let you build the text adventure, from inside the text adventure? Certainly for graphical virtual environments (MMO's, etc.) it is desirable to allow the world to be built and edited in real time. A text adventure one logical place to start that process.

There is a source code listing on the class website for a fragment of such a text adventure builder. Last time I taught games and virtual environments, students were asked to build out a fully-functional text adventure builder as their next homework! This time around I may add the text adventure builder to Chapter 7 of the Unicon Games Book, but I am not likely to make you write one. On the other hand, they are useful to study, and it might be good to design the content for a text adventure version of Treasure Island.

Googling "Treasure Island" and "text adventure" together it is clear that a lot of pirate-themed text adventures have been done before, including the 2nd title from Scott Adams, and apparently, a commercial game for the Commodore 64 that was actually based on Stevenson's novel.

Besides basic room design, and narrative story line (text), one of the main design issues is regarding state: how much must the system remember about the actions of the user in order to complete the adventure? Are all pieces of state simple booleans?

Text Adventure as Finite Automaton

class Room(name, descrip, detail, edges)
   # ... methods
initially(nm, desc, det)
    name := \nm | "unknown room"
    descrip := \desc | "You are in a nondescript empty room."
    detail := \det | "There is nothing here."
end

global rooms, current

procedure main()
   rooms := table()
   write("Welcome to the text adventure builder")
   current := rooms["void"] :=
       Room("void","You are in a dark void.","You can't see anything much.")

   repeat {
      # ... tell the situation (where the user is, etc.)
      # ... tell what the obvious actions/choices are.
      if not ( command := read() ) then stop("Goodbye.")
      argv := cmdlist(command)
      case argv[1] of {
	 # ... interpret user actions
	 }
      }
end

      write(current.descrip)
      every write((!\(current.edges)).descrip)

procedure cmdlist(s)
    L := [ ]
    trim(s,0) ? {
	while put(L, tab(upto(' \t'))) do {
	    while L[-1][1]=="\"" & L[-1][-1]~=="\"" do {
		L[-1] ||:= tab(many(' \t'))
		L[-1] ||:= tab(upto(' \t'))
	    }
	    if L[-1][1]=="\"" & L[-1][-1]~=="\"" then
		L[-1] := L[-1][2:-1]
	    tab(many(' \t'))
	}
	put(L, tab(0))
    }
    return L
end

Sim Games

• Hamurabi
• Taipan
• SimCity
• The Sims
• Sid Meier's Pirates!

Notes on Hamurabi

The main procedure simply creates one city instance and calls its play() method.

procedure main()
   Babylon().play()
end

class Babylon (
	Z, # Year
	D, # People died this turn
	D1, # People died, cumulative
	I, # Immigrants
	P, # Population
	P1, # Starvation percentage
	A, # Acres
	Y, # Yield
	E, # Eaten
	S, # Store
	C, # Random yearly yield modifier
	Q, # Input
	L, # Acres per person
	H
       )

method play()
    repeat {
	report()
	buy()
	sell()
	plant()
	harvest()
    }
end

method buy()
   Y := ?11 + 16
   write("Land is trading at " , Y , " bushels per acre.")
   repeat {
      writes("How many acres do you wish to buy? ")
      if not (Q := integer(read())) then {
	 write("Try using the newfangled Arabic digits, please.")
	 next
	 }
      if Q < 0 then finish("quit")
      else if Y * Q <= S then return
      else {
	 write("Hamurabi:  think again. You have only ", S)
	 write(" bushels of grain.  Now then,")
	 }
      }
end

Thoughts on Taipan

Lecture 5

Blurbs

Mailbag Q: Is there a self reference available in an object, as is available in a C++ object?

A: Yes, its name is self and it is seldom used. self.x is the same as x unless you had a local or parameter named x; self.m() is the same as m() unless you had a local or parameter named m. You can pass self as a parameter, insert it into lists and tables, etc. About the only place where self is usually required though is when you want to call a superclass method that has been overridden, as in self.superclassname.m()

Tips from an Office Hour Session

Windows Unicon doesn't like being installed in a path with spaces, such as \Program Files. It and a couple other bugs will likely be addressed in a new binary build sometime next week. :-)

CS 428/528 Forum

Topic "MMO Experiences" was added for those of you who plan to waive your HW#2 Part Two (which mainly means: try out Lord of the Rings Online with the class).

Achaea

Last class there was reference to this "text-based MMO". Of course, the term for "text-based MMO" is MUD, standing for Multi-User Dungeon or Multi-User Domain. MOO is also a synonym, more or less. Achaea appears to be web-based and slick, but I failed to create a character on my first try. Still it may be worth your checking out.

Battle for Wesnoth

I can already tell from a single screenshot that I am going to love Battle for Wesnoth...because it uses hex maps that remind me of some of my favorite old table-top wargames. Turn-based 2D graphics, a logical intermediate step between ASCII art games and 2D real-time games.

From Bruce Bolden

Bruce sent me a link to a Gamasutra article about Magicka's day #1 sales. This one was started as a student project. The point? With the right game idea and mad development skills, any one of you could make this happen here.

Taipan, cont'd

Thought exercise: what would it look like to merge Taipan's mechanics with Hamurabi's? Taipan fluctuates commodity prices at the cities randomly each turn. What would it take to tie commodity prices more intelligently to different forms of government, or different governing AI personalities (wise, lazy, warlike...)?

Rabin Game Design (part 1)

From Text to 2D

80x24 = 1920 possible positions per screen. As you can see from this nethack screenshot, each screen/level of rogue or nethack might provide 5-20 rooms, with more detailed navigation than a text adventure utilizes. Rogue had on the order of 17-25 such levels; nethack has far, far more. One thing I miss in nethack compared with text adventures is the detailed text description of the rooms; there is no real reason in a game like Pirate Duel why the current room or corridor you are in could not have a supporting text description.

Note the similarities between this and the new chapter 9 for the Unicon games book "Pirate Duel". See piraduel.icn and ship.dat.

Besides the "rogue-style" transition to text-mode as a low-resolution 2D graphics display, another intermediate point between the text mode games we have seen so far and the animated games that we will be discussing shortly are the early graphical adventures such as "The Secret of Monkey Island".

A graphical adventure of this sort simply substitutes a 2D image for the basic textual description of the current room. Note the easier-than-pie point-and-click menu of all the verbs that are allowed at any given point!

Comments on Homeworks

• First priority is of course correctness, then "look and feel"
• Beyond these, your goal is to create the most "elegant" solution. "Elegant" mostly means shortest but most readable. Try writing your program as poetry, even a limerick or haiku, instead of a novel. This affects maintainability and extensibility.

Arcade games

• smooth animation
• highly responsive user input
• gameplay highly repetitive
• based on speed and coordination

"Ping"

--> What is the fatal flaw in this immaculate code?

Initialization:

procedure main()
   &window := open("Ping","g", "size=640,480",
		   "bg=black", "fg=white")
   FillRectangle(10,220,10,40)
   FillRectangle(318,0,4,480)
   FillRectangle(620,220,10,40)
   FillRectangle(340,240,10,10) # ball
   x := 340
   y := 240
   dx := 1
   dy := 0
   p1x := 10
   p2x := 620
   p1y := p2y := 220
   p1score := p2score := 0

   repeat {
      # erase ball at old position
      EraseArea(x,y,10,10)
      FillRectangle(318,0,4,480)

      # calculate new position
      x +:= dx
      y +:= dy 
      # draw ball at new position
      FillRectangle(x,y,10,10)
      WSync()

      # bounce off paddles
      if p1x <= x <= p1x + 10 &
          p1y <= y+10 <= p1y + 40 then {
            dx := dx * -1
            dy +:= ((y+5) - (p1y+20))/15
          }
      if p2x <= x+10 <= p2x + 10 &
          p2y <= y+10 <= p2y + 40 then {
            dx := dx * -1
            dy +:= ((y+5) - (p2y+20))/15
          }
      # bounce off top or bottom wall
      if y <= 0 then dy := dy * -1
      if y+10 >= 480 then dy := dy * -1

      if x + 10 > 640 then {
         dx := dx * -1
         p1score +:= 1
         dy := 0
         GotoXY(10,10)
         writes(&window, p1score)
         }
      if x <= 0 then {
         dx := dx * -1
         p2score +:= 1
         dy := 0
         GotoXY(600,10)
         writes(&window, p2score)
         }

      delay(8)

      # move paddles up or down in response to user input
      if (* Pending() > 0) then {
         e := Event()
         if e == ("q"|"a") then {
	    EraseArea(p1x,p1y,10,40)
            if e == "q" then p1y -:= 5
            else p1y +:= 5
            FillRectangle(p1x,p1y,10,40)
	    }
         else if e == ("p"|"l") then {
	    EraseArea(p2x,p2y,10,40)
            if e == "p" then p2y -:= 5
            else p2y +:= 5
            FillRectangle(p2x,p2y,10,40)
	    }
         }
      }
   Event()
end

Arcade Games typically require lower-level input handling. Minimally, asking the operating system for separate "key press" and "key release" events. In unicon this is requested by the attribute assignment "inputmask=k". Key release events are negative integers (-ord(c)-128 for key c, where ord(c) is the ASCII code for character c).

Exercise: modify ping.icn to keep moving upwards as long as the paddle's "up" key is pressed, and stop when it is released.

lecture 6

Announcements

ECE Research Colloquium, Thursday 3:30 TLC044

"What can we learn about our bodies and minds by researching robotics?"

Microsoft Imagine Cup thingie, next Tuesday 4:30 JEB 328

free pizza. and hey, its Microsoft, so it must be good

Supplemental Lecture Notes

• Week 2 Notes are here
• This week: Gary Hollingshead

Head Check: How Many Have Working LOTRO Accounts ?

• Are we ready to have our official class MMO educational session yet?
• The server on which I can render the most assistance, and therefore recommend for class use, is named "Imladris".
• create a character there, and try to play it to level 10 or so
• meet at the "Prancing Pony" inn, in Bree.
• date and time for an in-game session: (tbd)

Rabin Game Design (part 2)

• We will cover the 2nd half of the Rabin 2.2 slides.

Tony Downey supplement

• Since we are talking about game design, you may also find this Tony Downey blog article interesting. Please read it. Thank Bruce. Key subpoints to consider (and agree or disagree with):
  • Prototype
  • Design is usually by trial and error, not by flashes of brilliance
  • Gameplay trumps content
  • Dynamic content trumps static content
  • Progress, Obstacles, Resources - the big three mechanics
  • Avoid perfectionism and NIH syndrome - you don't have to invent it all
  • [Jeffery] ... but canned game frameworks can overly constrain your game.
  • "variable driven development" - identify explicit simulation parameters. use variables, not constants. consider a runtime interface for tweaking them.
  • community -- high scores, in-game expressions of identity, status
  • power law -- free to play, sell add-ons later
  • collect and analyze player data
  • tutorial ? I thought Minecraft was lauded for not having a tutorial...
    • demo - learn by watching
    • guidepost - learn by in-game signs
    • sandbox - learn in a danger-proof environment
    • sensei - learn from a recurring relationship with a master

A Word on Unicon Objects

In Unicon...

class syntax was derived from record declaration syntax.

record foo(x,y) became

class foo(x,y)
   method m(z)
     ...
   end
end

inheritance is class foo : bar : baz (x,y) ...

superclasses bar and baz are looted, in that order, for stuff to add to foo. If its already "got one" you don't add that field/method. It is called "closure-based inheritance" and it is quite intuitive.

Class constructors are like record constructors: v := foo(1,2)

except that they execute an initially section if the class has one. If the initially section has a parameter list it overrides the default record-style binding of parameters to class fields.

No destructors

Garbage collection. You can by convention define your own explicit destructor protocol when needed. For example GUI widgets do so.

Method invocation is o.m(1,2,3)

except rarely when you use o$superclass.m(1,2,3)

Objects play nicely with Icon's structure types

Typical is objects with lists or tables of other objects...

Brick

--> What is the near-fatal flaw in this elegant code?

• Brick

class Brick(x, y, color)
   method score()
      return case color of {
		"blue": 10
		"yellow orange" : 5
	        "green": 1
         }
   end
   method draw()
      Fg(color)
      FillRectangle(x,y,45,20)
   end
   method erase()
      color := "black"
      EraseArea(x,y,45,20)
   end
   method hittest(ballx, bally)
      if color == "black" then fail
      if x-10 < ballx < x + 45 &
         y-10 < bally < y + 20 then return
      fail
   end
end

procedure main()
   bricks := [ ]
   &window := open("Bricks", "g",
		   "size=640,480",
                   "fg=white","bg=black")
   row := 0
   every row := 0 to 7 do {
      if row = 0 then
         color := "blue"
      else if 1 <= row <= 4 then
	 color := "yellow orange"
      else if row > 4 then color := "green"
      put(bricks, [ ] )
      every column := 0 to 12 do {
         b := Brick(column * 49 + 2,
		    row * 24 + 12, color)
         put(bricks[ -1 ], b)
         }
   }
   every (!!bricks).draw()
   Fg("white")

   FillRectangle(320,460,40,10)
   FillRectangle(320,260,10,10) # ball
   x := 320
   y := 260
   dx := 0
   dy := 1
   px := 320
   py := 460
   score := 0
   lives := 0

   repeat {
      # erase ball at old position
      EraseArea(x,y,10,10)

      # calculate new position
      x +:= dx
      y +:= dy 
      # draw ball at new position
      FillRectangle(x,y,10,10)
      WSync()
      # bounce off paddle
      if px <= x <= px + 40 &
          py <= y+10 <= py + 10 then {
            dy := dy * -1
            dx +:= ((x+5) - (px+20))/10
          }

      # bounce off left, right, or top wall
      if x <= 0 then dx := dx * -1
      if x+10 >= 640 then dx := dx * -1
      if y <= 0 then dy := dy * -1

      # take a life when the ball hits the bottom edge
      if y + 10 > 480 then {
         dy := dy * -1
         lives +:= 1
         dx := 0
	 if lives = 4 then {
	 WAttrib("label=Bricks [game over, q to quit] _
		 score: " || score)
	     while *Pending() > 0 do Event()
	     while Event() ~== "q"
	     exit(0)
	     }
         else
	 WAttrib("label=Bricks [" ||  lives || " / " ||
		"4] score: " || score)
         }

      every b := !!bricks do {
	  if b.hittest(x,y) then {
	      score +:= b.score()
	      b.erase()
	      WAttrib("label=Bricks [" || lives ||
		      " / " || "4] score: "|| score)
              dy *:= -1
	  }
      }

#      delay(1)
     every 1 to 75000

      # move paddle left or right in response to the user
      EraseArea(px,py,40,10)
      px := QueryPointer()
      FillRectangle(px,py,40,10)
      }
   Event()
end

Lecture 7.

Preliminary Comments on HW#2

• Submitted solutions by 20 students appear to be all over the map in terms of language, IDE, OS, compiler, library requirements. C++/Qt, Ruby/Gosu, ObjC/Cocoa, Virtools, etc. etc.
• Requirement is that I be able to compile and run your code.
• Burden of proof that you meet this requirement is on the student.
• As of 1pm, one student HW2 has met the burden of proof (Miller, on Apple)
• Mr. Norris, your instructions were good, thank you, I will have a go at it. So far, some other students have submitted assignments without adequate instructions, without makefiles, and without hope they will pass the burden of proof. :-)
• I am willing to legally install compilers/IDEs/libraries in order to grade your work. If I have to.
• I am not willing to pay for software in order to grade your work, nor (probably) to install a new OS in order to grade your work.

Quick Look at HW#3

Conway's Game of Life

• Simple rules can generate complex behaviors
• May provide suggestions or building blocks for self-balancing dynamic virtual worlds.

Cellular automata are sooooo cute. How do we get from them to, say, a civilization of Dwarves?

Step 1 might be to have them fight each other, as marketed by asterisksoft. There are similar, elaborated versions involving sharks and fishes.

Life Source Code

global limit  #  optional limit to number of generations

procedure main(args)
   n := args[1] | 25        # default is a 25x25 grid
   limit := args[2] | &null
   &window := open("life - Enter the starting pattern, end with EOF",
		   "g","size=450,450","font=typewriter,13")
   grid := getInitialGrid(n)
   play(grid)
end

# This procedure reads in the initial pattern, inserting it
#   into an nXn grid of cells.  The nXn grid also gets a
#   new border of empty cells, which just makes the test simpler
#   for determining what do with a cell on each generation.
# It would be better to let the user move the cursor and click
#   on cells to create/delete living cells, but this version
#   assumes a simple ASCII terminal.
procedure getInitialGrid(n)
   static notBlank, allStars
   initial {
      notBlank := ~' '
      allStars := repl("*",*notBlank)
      }

   g := list(n+2, repl(" ",n+2))        # store as an array of strings

   while (e := Event()) ~=== "q" do {
      if e === &lpress  then {
	   g[&row,&col] := toggle(g[&row,&col])
       }
      if e === &ldrag then {
	   g[&row,&col] := "*"
       }
      display(g)
   }

   return g
end

procedure toggle(s)
    if s === " " then return "*" else return " "
end

# Simple-minded procedure to 'play' Life from a starting grid.
procedure play(grid)
   while not allDone(grid) do {
      display(grid)
      if Event() === "q" then break
      grid := onePlay(grid)
      }
end

# Display the grid
procedure display(g)
   EraseArea()
   GotoRC(1,1)
   every write(&window, !g)
end

# Compute one generation of Life from the current one.
procedure onePlay(g)
   ng := copy(g)
   every ng[r := 2 to *g-1][c := 2 to *g-1] := case sum(g,r,c) of {
      3:       "*"     # cell lives (or is born)
      2:       g[r][c] # cell unchanged
      default: " "     # cell dead
      }
   return ng
end

# Return the number of living cells surrounding the current cell.
procedure sum(g,r,c)
   cnt := 0
   every (i := -1 to 1, j := -1 to 1) do
      if ((i ~= 0) | (j ~= 0)) & (g[r+i][c+j] == "*") then cnt +:= 1
   return cnt
end

# Check to see if all the cells have died or we've exceeded the
#   number of allowed generations.
procedure allDone(g)
   static count
   initial count := 0
   return ((count +:= 1) > \limit) | (trim(!g) == " ")
end

Rabin

Arcade Game Framework

# open window
repeat {
   # erase moving objects from their old positions
   # draw moving objects at their new positions
   # read user input
   # calculate all deaths, births, and changes in movement
}

Lecture 8

Career Fair

Supplemental Lecture Notes

• Week 3 Notes are here
• This week: Joel Kim
• Taking a quick peek at the schedule, if I missed your sign-up, please remind me when you would like to take notes.

HW#2 Comments

• A couple C++ (Qt, SDL...), 1 Ruby/Gosu, 1 ObjC/Cocoa, 1 Virtools, a couple VS, a few Unicon
• Visual Studio 2010 installed, working on various other langs/libs
• C++ FYI: <foo.h> implies foo.h is a system file. "foo.h" is a user file.
• IDEs: Qt 4.7 on Windows is really slick... but it does its dirty work off in a weird secret temp directory, almost as bad as Win Vista/7's shadow directories.
  
• Unicon: "I was having trouble getting the "link" command to work. It kept saying "icont: cannot resolve reference to file 'insert whatever file I'm trying to link.u'"

  Unicon works like C++, you must compile separate files with -c in order to link to them. The equivalent of .o files are .u files. You normally don't "link"-declare access to your own .u files, just list .u files on the link command line. Use "link" declarations for easy access to standard library modules. In theory the IDE has a multi-file project build facility. If that doesn't work your options are to report a bug please, or use "make". A "make" for Windows can be found here if you don't have one.

• Consider the following code abstracted from a past student howework submission:

  L := ["bullets", "rice", "beans"]
  flag := 0
  every
     {
     if !L == "beans" then flag := 1
     }
  

  I will say: this code works. What is interesting about it?

HW#2 Evaluation Status Update

• Cody Miller, on Apple. 1 KLOC of ObjC/Cocoa.
  
  
  • Cute, nice piratey dialog, no action.
• BCK's Virtools. ?? KLOC. 52MB. violin music. side-scroller-feel.
  
  • Cute, no action.
• Max Stillwell's 1.5 KLOC of C++/Qt.
  
• Doug Drobny's, 660 LOC of C++/curses
  
• Jacob Flynn's 330 lines of Unicon
  
  
• Nathan Mazur's 800 lines of Unicon
  
  • Four pirates in an extensible pirate npc config data file format.
• Dallas Stinger's 2750 lines of C#
  • Ship to ship combat, sort of; boats move/sail a bit.
• Brett Hitchcock's 390 lines of C++ with SDL
  
• Zach Kimball's 1.9K lines of Python with PyQt
  
  
• Jamie Nance's 572 lines of Unicon
  
• Daniel Norris's 360 lines of Ruby with GOSU

Rabin of the Day

I am biased about just how neanderthal the games industry has traditionally been in terms of languages and tools. Lots of early games were written in BASIC and were slow. After, DOOM, when speed ruled on non-GPU hardware, the dinosaur-mentality was somewhat excuseable. I have old books on "Game Programming" which are really VGA assembler language trickbooks.

Sesrit

• Sesrit

...
/&window := WOpen("label=sesrit","size=276,510", "posx=20")
colors := table(&window)
every c := ("blue"|"yellow"|"cyan"|"green"|"red"|"white"|
            "red-yellow" | "purple-magenta" | "pink") do
         colors[c] := Clone("fg=" || c)

   L := list(30)
   every !L := list(10, "black")

How does the following game loop compare with the Arcade Framework that I proposed above?

procedure game_loop()
   game_status := 1
   repeat {
      while *Pending() > 0 do {
         case Event() of {
            Key_Left  : move_piece(-1, 0)
            Key_Right : move_piece(1, 0)
            Key_Down  : rotate_piece(1, -1)
            Key_Up    : rotate_piece(-1, 1)
            " "       : while move_piece(0,1) # drop piece to bottom
            "q"       : if &meta then exit()
            "a"       : if &meta then about_sesrit()
            "p"       : if (&meta & game_status = 1) then pause()
            "n"       : if &meta then return

            &lpress   : {
               if 15 <= &x <= 105 then {
                  if 270 <= &y <= 290 then pause()
                     else if 300 <= &y <= 320 then return
                        else if 360 <= &y <= 380 then
                           about_sesrit()
                  }
               }
            &lrelease :
               if ((15 <= &x <= 105) & (330 <= &y <= 350)) then
                  exit()
            }
         }
      if not move_piece(0,1) then {
	 if (!activecells)[1] < 2 then {
            game_over()
            return
            }
         # if we couldn't drop the piece down, insert a new piece
	 }
      # ... misc. step code

      WSync()
      delay(delaytime)
      }
end

   ...
   case nextcolor := ?["red-yellow", "red", "yellow", "green",
                       "cyan", "blue", "purple-magenta"] of {
   "red-yellow":     nextpiece := [ [1,5], [1,6], [2,5], [2,6] ]
   "yellow":         nextpiece := [ [2,6], [1,6], [2,5], [2,7] ]
   "blue":           nextpiece := [ [2,6], [1,5], [2,5], [2,7] ]
   "purple-magenta": nextpiece := [ [2,6], [1,7], [2,5], [2,7] ]
   "red":            nextpiece := [ [3,6], [1,6], [2,6], [4,6] ]
   "green":          nextpiece := [ [2,6], [1,5], [1,6], [2,7] ]
   "cyan":           nextpiece := [ [2,6], [1,6], [1,7], [2,5] ]
   }

GUI's

• Custom GUI built into engine?
• Tweaks to both sides to play together nicely?

Mailbag

I created my LOTRO character on the wrong server, what do I do?

According to one website I read, transferring a character to another server costs $24.95. Presumably it is done through the LOTRO store. Another webpage I read said that its only allowed if the server you are transferring to is not overcrowded. Imladris is not overcrowded but you may prefer to just create a new character.

I didn't get to participate in last night's session! What do I do?

Although I will be playing LOTRO all semester and would be happy to schedule additional sessions by appointment, you are welcome to get your MMO experience with or without the company of your classmates or instructor. Please learn enough about MMO's to cover the topics mentioned in HW-LOTRO.

How do I get the y value from QueryPointer()?

QueryPointer() is documented in "Graphics Programming in Icon". It is a generator. You can say

   L := []; every put(L, QueryPointer())

or if you want to be gross:

   every y := QueryPointer() do /x := y

Think and ask questions if you don't "get" this one.

Rivendell Report

We headed unevenfully out of Bree on the main road (not avoiding Black Riders like Frodo had to), past the Forsaken Inn, from which point we had some fun swarming to kill things that would have wiped us out individually. We had one really good minstrel (Vil.); the other minstrel (Godivadoc) was not acting like one.

We got to the last bridge and entered the Trollshaws, and quickly were wiped out. Level 10 characters in a level 30-something zone attract even the flies and the deer to swarm and attack. A level 25 healer can neither heal fast enough nor stay alive, when the party is attacked by several level 33 monsters at once. After being killed, if you are beneath a certain level, you restart at home 1000+ miles away, even if you are "revived" by a healer's so-called resurrection spell.

Eventually, we resorted to an escort by a level 39 hunter and 38 champion, and even they were not able to keep the whole party alive in the face of constant swarming attacks by all animals within range. We had to fall back on the "pirate's code", and press on. In the end, 5 students (I think) made it to Rivendell, but only after multiple deaths and with the assistance of a 7th grader staying up past his bedtime. Rivendell is of course a major resort destinations, with glamorous celebrities, spas, elven forges and the like. Kudos to those who made it, and apologies to those who fell behind.

GUIs in Games

• You may want a Graphical User Interface (GUI) for your arcade or strategy games.
• Key issue: how are GUI components and graphics mixed?

  if you are real, real lucky, your language/engine does it for you

  and doesn't leave you stuck in a limited-option world

  graphics-primitives-are-GUI-widgets model

  pain to write a new widget for every graphical entity in a game

  build custom GUI using graphics primitives

  pain to develop enough GUI from scratch

  independent-subwindow "view" approach

  moderately easy to mashup a Frankeninterface; looks a bit old school. Compare early EverQuest with later MMOs.

GUIs in Unicon

Basic principles of Unicon GUIs. How does your chosen language do the comparables?

Dialog

The root of GUI components, tied to a window.

Component

Superclass of all widgets. Contains subwidgets. Tree of Clone()s.

Listeners and event-driven programming

Dispatcher, show_modal() vs. show_modeless()

Rabin of the Day

• I have allowed students to turn in assignments using Flash before. They were competitive with solutions done by other students.
• I am not a fan of proprietary or semi-proprietary languages like Flash
• I feel similarly about Virtools.
• I am real nervous...
  • if the end product won't run on all my platforms
  • if I am a slave to vendor lock-in;
  • if I can't control whether I will still be able to make changes and compile my programs in 10 years...

Blasteroids

bash-3.2$ wc -l *.icn
   91 aboutbox.icn
  289 blaster.icn
  756 game.icn
  428 optionsdialog.icn
 1564 total

blaster: blaster.u game.u optionsdialog.u aboutbox.u
	unicon blaster.u game.u optionsdialog.u aboutbox.u

blaster.u: blaster.icn
	unicon -c blaster

game.u: game.icn
	unicon -c game

aboutbox.u: aboutbox.icn
	unicon -c aboutbox

optionsdialog.u: optionsdialog.icn
	unicon -c optionsdialog

• aboutbox.icn is 92 lines.
• Almost all machine-generated by Ivib.
• Actual Ivib data is contained in an enormous multiline comment at end.
• Old application, required migration between the older Version 1 GUI classes and newer version 2.
• Major difference between V1 and V2 Unicon GUIs: a "dialog_event" method was replaced by a Listener architecture. Non-issue for you folks.

import gui
$include "guih.icn"
class dialogabout : Dialog(text_button_1, text_list_1)
   method handle_text_button_1(ev)
	dispose()
   end

   method handle_text_list_1(ev)
   end

   method handle_default(ev)
   end

   method dialog_event(ev)
      case ev.get_component() of {
         text_button_1 : handle_text_button_1(ev)
         text_list_1 : handle_text_list_1(ev)
         default : handle_default(ev)
      }
   end

   method init_dialog()
   end

   method end_dialog()
   end

   method handle_v2_events(ev)
      dialog_event(V2TOV1(ev))
   end

   method setup()
      self.set_attribs("size=250,150", "bg=pale gray")
      text_button_1 := TextButton()
      text_button_1.set_pos("122", "123")
      text_button_1.set_align("c", "t")
      text_button_1.connect(self, "handle_v2_events", &null)
      text_button_1.clear_toggles()
      text_button_1.set_label("Okay")
      text_button_1.set_internal_alignment("c")
      self.add(text_button_1)
      text_list_1 := TextList()
      text_list_1.set_pos("26", "5")
      text_list_1.set_size("200", "75%")
      text_list_1.set_draw_border()
      text_list_1.connect(self, "handle_v2_events", &null)
      text_list_1.set_select_many()
      text_list_1.set_contents(["Blasteroids ", "by Jared Kuhn and Clint Jeffery", "Version 2.0", ""])
      self.add(text_list_1)
      self.connect(self, "handle_v2_events", &null)
   end

   method component_setup()
      self.setup()
   end

   initially
      self.Dialog.initially()
end

### Ivib-v2 layout ##
#class|Canvas|17|Name Table|table|integer|0|2|string|text_button|intege
#r|1|string|text_list|integer|1|SuperClass Name|string|Dialog|Import Na
#me|string|gui|Button Groups|class|ButtonGroupSet|2|Parent Canvas|1|Box
#es|list|0|Checkbox Groups|class|CheckBoxGroupSet|2|Parent Canvas|1|Box
#es|list|0|Gen Indent|integer|3|Gen Main|integer|1|Gen Component Setup|
#integer|1|Gen Init Dialog|integer|1|Gen Initially|integer|1|Dialog Str
#uct|class|CDialog|4|Min Width|null|Min Height|null|Ticker Rate|null|At
#tribs|list|1|string|bg=pale gray|Name|string|dialogabout|Width|integer
#|250|Height|integer|150|Items|list|2|class|CanvasTextButton|36|Parent 
#Canvas|1|Name|string|text_button_1|Class Name|string|TextButton|Import
# Name|string|gui|X Fix|null|Y Fix|null|W Fix|null|H Fix|null|W Default
#|integer|1|H Default|integer|1|X Spec|string|122|Y Spec|string|123|W S
#pec|integer|48|H Spec|integer|23|X Align|string|c|Y Align|string|t|Is 
#shaded|null|Is Button Subclass|integer|1|Draw Border|null|Attribs|list
#|0|Tooltip|null|Accel|null|Event Handlers|list|1|list|2|string|&null|s
#tring|handle_v2_events|Class Variable|integer|1|Parent Component|1|Lab
#el|string|Okay|No Keyboard|null|Img Up|null|Img Down|null|Img Width|nu
#ll|Img Height|null|Is Checked Flag|null|Is Checkbox Flag|null|Parent C
#heckBoxGroup|null|Parent Button Group|null|Internal Align|string|c|cla
#ss|CanvasTextList|29|Parent Canvas|1|Name|string|text_list_1|Class Nam
#e|string|TextList|Import Name|string|gui|X Fix|null|Y Fix|null|W Fix|n
#ull|H Fix|null|W Default|null|H Default|null|X Spec|string|26|Y Spec|s
#tring|5|W Spec|string|200|H Spec|string|75%|X Align|string|l|Y Align|s
#tring|t|Is shaded|null|Is Button Subclass|null|Draw Border|integer|1|A
#ttribs|list|0|Tooltip|null|Accel|null|Event Handlers|list|1|list|2|str
#ing|&null|string|handle_v2_events|Class Variable|integer|1|Parent Comp
#onent|1|Select One|null|Select Many|integer|1|Checked|list|4|null|null
#|null|null|Contents|list|4|string|Blasteroids |string|by Jared Kuhn an
#d Clint Jeffery|string|Version 2.0|string||Initial Focus|null|Event Ha
#ndlers|list|1|list|2|string|&null|string|handle_v2_events|

Blaster.icn

#
# blaster.icn - main module for Kuhn and Jeffery's Blasteroids
#
import gui
$include "guih.icn"

class blaster : Dialog(
   text_menu_item_3, text_menu_item_2, text_menu_item_1, text_menu_item_6,
   check_box_menu_item_1, check_box_menu_item_2,
   text_menu_item_5, text_menu_item_4, 
   roids, optionsbox, doneoptions)

   method handle_text_menu_item_3(ev)
      roids.tapped := 2
      roids.gamestart := 1
      roids.handle_event()
   end

   method handle_text_menu_item_2(ev)
   end

   method handle_text_menu_item_1(ev)
      dispose()
   end

   method handle_text_menu_item_6(ev)
      if doneoptions = 0 then {
	 doneoptions := 1
	 optionsbox.num_ships := 3
	 optionsbox.num_range := 10
	 optionsbox.chk_explode := (1=1)
	 optionsbox.chk_sound := &null
	 optionsbox.num_torpedos := 3
	 optionsbox.num_speed := 5
	 optionsbox.num_rotation := 5
	 optionsbox.num_level := 1
	 }
      optionsbox.show_modal()
      if optionsbox.hitokay = 1 then {
	 optionsbox.hitokay := 0
	 roids.num_ships := optionsbox.num_ships
	 roids.num_range := optionsbox.num_range 
	 roids.chk_explode := optionsbox.chk_explode
	 roids.chk_sound := optionsbox.chk_sound
	 roids.num_torpedos := optionsbox.num_torpedos
	 roids.num_speed := optionsbox.num_speed
	 roids.num_rotation := optionsbox.num_rotation
	 roids.num_level := optionsbox.num_level
	 }
   end

   method handle_check_box_menu_item_1(ev)
   end

   method handle_check_box_menu_item_2(ev)
      if f := open("highscor") then {
	  L := [ ]
	  while put(L, read(f))
	  close(f)
	  sort(L)
	  write("HIGH SCORES:")
	  every write(!L)
      }
   end

   method handle_text_menu_item_5(ev)
   end

   method handle_text_menu_item_4(ev)
	dialogabout().show_modal()
   end

   method handle_default(ev)
   end

   method dialog_event(ev)
      case ev.get_component() of {
         text_menu_item_3 : handle_text_menu_item_3(ev)
         text_menu_item_2 : handle_text_menu_item_2(ev)
         text_menu_item_1 : handle_text_menu_item_1(ev)
         text_menu_item_6 : handle_text_menu_item_6(ev)
         check_box_menu_item_1 : handle_check_box_menu_item_1(ev)
         check_box_menu_item_2 : handle_check_box_menu_item_2(ev)
         text_menu_item_5 : handle_text_menu_item_5(ev)
         text_menu_item_4 : handle_text_menu_item_4(ev)
         default : handle_default(ev)
      }
   end

   method init_dialog()
      WAttrib(win, "inputmask=k")
      set_ticker(1)
   end

   method end_dialog()
   end

   method handle_v2_events(ev)
      dialog_event(V2TOV1(ev))
   end

   method tick()
      roids.idle_func()
   end
   
   method setup()
      local menu_1, menu_2, menu_3, menu_bar_1, menu_separator_1
      self.set_attribs("size=500,500", "bg=pale gray")
      menu_bar_1 := MenuBar()
      menu_bar_1.set_pos("0", "0")
      menu_1 := Menu()
      menu_1.set_label("Game")
      text_menu_item_3 := TextMenuItem()
      text_menu_item_3.set_label("New")
      text_menu_item_3.connect(self, "handle_v2_events", ACTION_EVENT)
      menu_1.add(text_menu_item_3)
      text_menu_item_2 := TextMenuItem()
      text_menu_item_2.set_label("High Scores...")
      text_menu_item_2.connect(self, "handle_v2_events", ACTION_EVENT)
      menu_1.add(text_menu_item_2)
      text_menu_item_1 := TextMenuItem()
      text_menu_item_1.set_label("Quit")
      text_menu_item_1.connect(self, "handle_v2_events", ACTION_EVENT)
      menu_1.add(text_menu_item_1)
      menu_bar_1.add(menu_1)
      menu_2 := Menu()
      menu_2.set_label("Options")
      text_menu_item_6 := TextMenuItem()
      text_menu_item_6.set_label("Games Options...")
      text_menu_item_6.connect(self, "handle_v2_events", ACTION_EVENT)
      menu_2.add(text_menu_item_6)
      check_box_menu_item_1 := CheckBoxMenuItem()
      check_box_menu_item_1.set_label("Sound")
      check_box_menu_item_1.connect(self, "handle_v2_events", ACTION_EVENT)
      check_box_menu_item_1.set_is_checked()
      menu_2.add(check_box_menu_item_1)
      check_box_menu_item_2 := CheckBoxMenuItem()
      check_box_menu_item_2.set_label("Explosions")
      check_box_menu_item_2.connect(self, "handle_v2_events", ACTION_EVENT)
      check_box_menu_item_2.set_is_checked()
      menu_2.add(check_box_menu_item_2)
      menu_bar_1.add(menu_2)
      menu_3 := Menu()
      menu_3.set_label("Help")
      text_menu_item_5 := TextMenuItem()
      text_menu_item_5.set_label("Game Play...")
      text_menu_item_5.connect(self, "handle_v2_events", ACTION_EVENT)
      menu_3.add(text_menu_item_5)
      menu_separator_1 := MenuSeparator()
      menu_separator_1.set_is_shaded()
      menu_3.add(menu_separator_1)
      text_menu_item_4 := TextMenuItem()
      text_menu_item_4.set_label("About...")
      text_menu_item_4.connect(self, "handle_v2_events", ACTION_EVENT)
      menu_3.add(text_menu_item_4)
      menu_bar_1.add(menu_3)
      self.add(menu_bar_1)
      roids := Blasteroids_Game()
      roids.set_pos("0", "26")
      roids.set_size("100%", "100%-26")
      self.add(roids)
      self.connect(self, "handle_v2_events", &null)
   end

   method component_setup()
      self.setup()
   end

   initially
      optionsbox := optionsdialog()
      doneoptions := 0
      self.Dialog.initially()
end

procedure main()
   local d
   d := blaster()
   d.show_modal()
end

### Ivib-v2 layout ##
#class|Canvas|17|Name Table|table|integer|0|6|string|check_box_menu_ite
#m|integer|2|string|custom|integer|1|string|menu|integer|3|string|menu_
#bar|integer|1|string|menu_separator|integer|1|string|text_menu_item|in
#teger|6|SuperClass Name|string|Dialog|Import Name|string|gui|Button Gr
#oups|class|ButtonGroupSet|2|Parent Canvas|1|Boxes|list|0|Checkbox Grou
#ps|class|CheckBoxGroupSet|2|Parent Canvas|1|Boxes|list|0|Gen Indent|in
#teger|3|Gen Main|integer|1|Gen Component Setup|integer|1|Gen Init Dial
#og|integer|1|Gen Initially|integer|1|Dialog Struct|class|CDialog|4|Min
# Width|null|Min Height|null|Ticker Rate|null|Attribs|list|1|string|bg=
#pale gray|Name|string|blaster|Width|integer|500|Height|integer|500|Ite
#ms|list|2|class|CanvasMenuBar|26|Parent Canvas|1|Name|string|menu_bar_
#1|Class Name|string|MenuBar|Import Name|string|gui|X Fix|null|Y Fix|nu
#ll|W Fix|null|H Fix|null|W Default|integer|1|H Default|integer|1|X Spe
#c|string|0|Y Spec|string|0|W Spec|string|100%|H Spec|integer|23|X Alig
#n|string|l|Y Align|string|t|Is shaded|null|Is Button Subclass|null|Dra
#w Border|null|Attribs|list|0|Tooltip|null|Accel|null|Event Handlers|nu
#ll|Class Variable|null|Parent Component|1|Menus|list|3|class|CanvasMen
#u|17|Name|string|menu_1|Class Name|string|Menu|Import Name|string|gui|
#Accel|null|Label|string|Game|Label Left|null|Label Right|null|Is shade
#d|null|Img Left|null|Img Left Width|null|Img Left Height|null|Img Righ
#t|string|9,c1,0~~~~~~~~000~~~~~~00000~~~~0000000~~0000000000000000~~00
#000~~~~000~~~~~~0~~~~~~~~|Img Right Width|integer|9|Img Right Height|i
#nteger|9|Event Method|null|Class Variable|null|Children|list|3|class|C
#anvasTextMenuItem|16|Name|string|text_menu_item_3|Class Name|string|Te
#xtMenuItem|Import Name|string|gui|Accel|null|Label|string|New|Label Le
#ft|null|Label Right|null|Is shaded|null|Img Left|null|Img Left Width|n
#ull|Img Left Height|null|Img Right|null|Img Right Width|null|Img Right
# Height|null|Event Method|string|handle_v2_events|Class Variable|integ
#er|1|class|CanvasTextMenuItem|16|Name|string|text_menu_item_2|Class Na
#me|string|TextMenuItem|Import Name|string|gui|Accel|null|Label|string|
#High Scores...|Label Left|null|Label Right|null|Is shaded|null|Img Lef
#t|null|Img Left Width|null|Img Left Height|null|Img Right|null|Img Rig
#ht Width|null|Img Right Height|null|Event Method|string|handle_v2_even
#ts|Class Variable|integer|1|class|CanvasTextMenuItem|16|Name|string|te
#xt_menu_item_1|Class Name|string|TextMenuItem|Import Name|string|gui|A
#ccel|null|Label|string|Quit|Label Left|null|Label Right|null|Is shaded
#|null|Img Left|null|Img Left Width|null|Img Left Height|null|Img Right
#|null|Img Right Width|null|Img Right Height|null|Event Method|string|h
#andle_v2_events|Class Variable|integer|1|class|CanvasMenu|17|Name|stri
#ng|menu_2|Class Name|string|Menu|Import Name|string|gui|Accel|null|Lab
#el|string|Options|Label Left|null|Label Right|null|Is shaded|null|Img 
#Left|null|Img Left Width|null|Img Left Height|null|Img Right|string|9,
#c1,0~~~~~~~~000~~~~~~00000~~~~0000000~~0000000000000000~~00000~~~~000~
#~~~~~0~~~~~~~~|Img Right Width|integer|9|Img Right Height|integer|9|Ev
#ent Method|null|Class Variable|null|Children|list|3|class|CanvasTextMe
#nuItem|16|Name|string|text_menu_item_6|Class Name|string|TextMenuItem|
#Import Name|string|gui|Accel|null|Label|string|Games Options...|Label 
#Left|null|Label Right|null|Is shaded|null|Img Left|null|Img Left Width
#|null|Img Left Height|null|Img Right|null|Img Right Width|null|Img Rig
#ht Height|null|Event Method|string|handle_v2_events|Class Variable|int
#eger|1|class|CanvasCheckBoxMenuItem|20|Name|string|check_box_menu_item
#_1|Class Name|string|CheckBoxMenuItem|Import Name|string|gui|Accel|nul
#l|Label|string|Sound|Label Left|null|Label Right|null|Is shaded|null|I
#mg Left|string|(b=black;0=shadow;1=hilite;~=trans)13,c6,~~~~~~~~~~~~~~
#00000000001~~00000000001~~00~~~~~~~11~~00~bbbbb~11~~00~bbbbb~11~~00~bb
#bbb~11~~00~bbbbb~11~~00~bbbbb~11~~00~~~~~~~11~~01111111111~~1111111111
#1~~~~~~~~~~~~~~|Img Left Width|integer|13|Img Left Height|integer|13|I
#mg Right|null|Img Right Width|null|Img Right Height|null|Event Method|
#string|handle_v2_events|Class Variable|integer|1|Img Up|string|(0=shad
#ow;1=hilite;~=trans)13,c6,~~~~~~~~~~~~~~11111111111~~11111111110~~11~~
#~~~~~00~~11~~~~~~~00~~11~~~~~~~00~~11~~~~~~~00~~11~~~~~~~00~~11~~~~~~~
#00~~11~~~~~~~00~~11000000000~~10000000000~~~~~~~~~~~~~~|Img Down|strin
#g|(b=black;0=shadow;1=hilite;~=trans)13,c6,~~~~~~~~~~~~~~00000000001~~
#00000000001~~00~~~~~~~11~~00~bbbbb~11~~00~bbbbb~11~~00~bbbbb~11~~00~bb
#bbb~11~~00~bbbbb~11~~00~~~~~~~11~~01111111111~~11111111111~~~~~~~~~~~~
#~~|Is Checked Flag|integer|1|Parent CheckBoxGroup|null|class|CanvasChe
#ckBoxMenuItem|20|Name|string|check_box_menu_item_2|Class Name|string|C
#heckBoxMenuItem|Import Name|string|gui|Accel|null|Label|string|Explosi
#ons|Label Left|null|Label Right|null|Is shaded|null|Img Left|string|(b
#=black;0=shadow;1=hilite;~=trans)13,c6,~~~~~~~~~~~~~~00000000001~~0000
#0000001~~00~~~~~~~11~~00~bbbbb~11~~00~bbbbb~11~~00~bbbbb~11~~00~bbbbb~
#11~~00~bbbbb~11~~00~~~~~~~11~~01111111111~~11111111111~~~~~~~~~~~~~~|I
#mg Left Width|integer|13|Img Left Height|integer|13|Img Right|null|Img
# Right Width|null|Img Right Height|null|Event Method|string|handle_v2_
#events|Class Variable|integer|1|Img Up|string|(0=shadow;1=hilite;~=tra
#ns)13,c6,~~~~~~~~~~~~~~11111111111~~11111111110~~11~~~~~~~00~~11~~~~~~
#~00~~11~~~~~~~00~~11~~~~~~~00~~11~~~~~~~00~~11~~~~~~~00~~11~~~~~~~00~~
#11000000000~~10000000000~~~~~~~~~~~~~~|Img Down|string|(b=black;0=shad
#ow;1=hilite;~=trans)13,c6,~~~~~~~~~~~~~~00000000001~~00000000001~~00~~
#~~~~~11~~00~bbbbb~11~~00~bbbbb~11~~00~bbbbb~11~~00~bbbbb~11~~00~bbbbb~
#11~~00~~~~~~~11~~01111111111~~11111111111~~~~~~~~~~~~~~|Is Checked Fla
#g|integer|1|Parent CheckBoxGroup|null|class|CanvasMenu|17|Name|string|
#menu_3|Class Name|string|Menu|Import Name|string|gui|Accel|null|Label|
#string|Help|Label Left|null|Label Right|null|Is shaded|null|Img Left|n
#ull|Img Left Width|null|Img Left Height|null|Img Right|string|9,c1,0~~
#~~~~~~000~~~~~~00000~~~~0000000~~0000000000000000~~00000~~~~000~~~~~~0
#~~~~~~~~|Img Right Width|integer|9|Img Right Height|integer|9|Event Me
#thod|null|Class Variable|null|Children|list|3|class|CanvasTextMenuItem
#|16|Name|string|text_menu_item_5|Class Name|string|TextMenuItem|Import
# Name|string|gui|Accel|null|Label|string|Game Play...|Label Left|null|
#Label Right|null|Is shaded|null|Img Left|null|Img Left Width|null|Img 
#Left Height|null|Img Right|null|Img Right Width|null|Img Right Height|
#null|Event Method|string|handle_v2_events|Class Variable|integer|1|cla
#ss|CanvasMenuSeparator|16|Name|string|menu_separator_1|Class Name|stri
#ng|MenuSeparator|Import Name|string|gui|Accel|null|Label|null|Label Le
#ft|null|Label Right|null|Is shaded|integer|1|Img Left|null|Img Left Wi
#dth|null|Img Left Height|null|Img Right|null|Img Right Width|null|Img 
#Right Height|null|Event Method|null|Class Variable|null|class|CanvasTe
#xtMenuItem|16|Name|string|text_menu_item_4|Class Name|string|TextMenuI
#tem|Import Name|string|gui|Accel|null|Label|string|About...|Label Left
#|null|Label Right|null|Is shaded|null|Img Left|null|Img Left Width|nul
#l|Img Left Height|null|Img Right|null|Img Right Width|null|Img Right H
#eight|null|Event Method|string|handle_v2_events|Class Variable|integer
#|1|class|CanvasCustom|25|Parent Canvas|1|Name|string|roids|Class Name|
#string|Blasteroids_Game|Import Name|string|gui|X Fix|null|Y Fix|null|W
# Fix|null|H Fix|null|W Default|null|H Default|null|X Spec|string|0|Y S
#pec|string|26|W Spec|string|100%|H Spec|string|100%-26|X Align|string|
#l|Y Align|string|t|Is shaded|null|Is Button Subclass|null|Draw Border|
#null|Attribs|list|0|Tooltip|null|Accel|null|Event Handlers|list|0|Clas
#s Variable|integer|1|Parent Component|1|Initial Focus|null|Event Handl
#ers|list|1|list|2|string|&null|string|handle_v2_events|

Clarification of the size of worlds

• According to wiki answers: earth's radius is 3961 miles; its circumference is 25k+. Thanks Bruce.
• According to a battle.net forum one of the many estimates of the size of the World of Warcraft is: around 8 miles in radius.
• Accepting that it is scaled for our convenience from some fictional planet that is comparable in size to earth, the "scaling for our convenience" is ~500x. As far as I know that is not counting the Outland you can port to, which is a set of fragments of the Orcs' home world.
• It is reasonable to ask questions like: is 500x the optimal scaling number for virtual worlds? Suppose that people want more content -- more surface area? What additional game mechanics would that call for?
• Where scaling gets interesting is when scaling of sizes/distances triggers issues in scaling of time -- real time or game time.
• Lotro abstracts away time/space trade-offs using "Travel Rations". You buy and eat travel rations to ignore months-long travel. Are there better ways to accomplish such scale-tweaks?
• When gamers want not just a virtual planet, but a virtual galaxy, what are the implications for a virtual environment? How successful have games been at feeling "galactic" in scope?
• WoW doesn't feel like it is a 500x scale. "Scale" in games might be 1:1 in some areas, 50x or 500x in others, or logarithmic if you have a really large space to deal with. See research papers on "graphical fisheye views of graphs" for dynamic nonlinear scales one could adopt in games.
• Suppose a virtual world designer wanted to dynamically tweak the scale as new content is introduced? Suppose a game mechanic included a "Zoom" mechanism? What might it look like?

Rabin

• Chapter 3.4, Programming Fundamentals.

Blasteroids, cont'd

game.icn

import gui
$include "keysyms.icn"
$define MAXHEIGHT 572		#playfield height/width dimensions
$define MAXWIDTH  500
$define VOFFSET   60
$define VSTARSOFF VOFFSET-36
$define SPEEDINC  0.1		#acceleration constant
$define MAXSPEED  5.0		#maximum speed
$define NEGMAXSPEED -5.0	#negative of max speed
$define RPTMIN    7
$define RMINSIZE  15	#min asteroid size (pixels)
$define RMAXSIZE  30	#max asteroid size (pixels)
$define ROIDPROBABILITY 960 # interval of new asteroids (lower=more)
$define MAXROIDS  10	#maximum allowed number of asteroids
$define RMAXSPEED 2.5	#maximum speed of asteroids
$define MAXBLASTS 10 	#no more than this many laser blasts at a time
$define MAXBLASTRANGE 40 #how far the blasts travel before they fizzle out
$define BLAST_RADIUS 36	#how far away a legal collision is from an asteroid
$define DELAY_TIME 33 	#length of a timeslice (milliseconds)

record point(x,y) #a point on the screen

record rtrack( 	#asteroid tracking record
   x, y, 	#center coordinates
   angle, 	#angle of rotation (not used)
   points, 	#array polygon point coordinates (relative to the center)
   size, speed, 	#size / speed of asteroid
   offset, 	#precomputed multiplier, saves computations
   offset2x, 	#same
   active)	#boolean, active or not

record btrack(	#blast tracking record
   x, y, 	#center coordinates
   angle, 	#angle of rotation of blast
   flag, 	#active / inactive
   traveled,	#how far the blast has gone
   deactnext)	#flag this to be deactivated next time slice

class Blasteroids_Game : Component(
   starsdone, # initialization flag
   tapped,
   gamestart,
   shipx, shipy,
   c,
   newwin, backwin,
   lookups, lookupc,
   currblast, blasts, blastwin,
   roids, currroids, roidwin,
   explodewins, shiphit,
   speedx, speedy,
   angle, currspeed,
   oldshipx, oldshipy,
   masterspeed, oldangle,
   negx, negy,
   redrawship,
   x1, y1,
   firsttime,
   livesleft, livesdone,
   score, oldscore,
   num_ships, num_range,
   chk_explode, chk_sound,
   num_torpedos, num_speed,
   num_rotation, num_level,
   left_pressed, right_pressed,
   up_pressed, down_pressed)

   method display()
      if starsdone = 0 then {
	 drawstars()
	 newwin := cwin
	 explodewins := []
	 every put(explodewins, Clone(newwin,"fg=" ||
	    ("red"|"orange"|"orangish red"|"black"|"white")))

	 &window := newwin

	 CopyArea(newwin, backwin, 0, 0, MAXWIDTH, MAXHEIGHT)
         }
   end

   method drawstars()
      starclones := []
      every put(starclones, Clone(cwin,"fg=" ||
	 ("vivid white"|"gray"|"light gray"|"dark gray"|"black")))
      FillRectangle(starclones[5], 0, VSTARSOFF, MAXWIDTH, MAXHEIGHT)
	
      #at every point...
      every (x_loc := 0 to MAXWIDTH, y_loc := 0 to 3) do {
	 #draw a randomly colored star in a random location
	 DrawPoint(starclones[(?100-1)/25+1], x_loc, ?500 + VOFFSET)
         }
      newwin := cwin
      CopyArea(newwin, backwin, 0, 0, MAXWIDTH, MAXHEIGHT)
      starsdone := 1
   end

   method reset_everything()
      eraseship()
      eraseblasts()
      eraseroids()
      currblast := 0
      currroids := 0
      redrawship := 5
      x1 := (MAXWIDTH / 2)
      shipx := (MAXWIDTH / 2)
      y1 := (MAXHEIGHT / 2)
      shipy := (MAXHEIGHT / 2)

      #and going nowhere
      speedx := 0
      speedy := 0
      masterspeed := 0
      oldshipx := 0
      oldshipy := 0

      #flag, (0 or 1), if the ship is drawn, the delay has already been
      # done, otherwise, we delay when the blasts / asteroids are done       

      # number of times to redraw the ship when it isn't moving
      redrawship := 5

      #angle of the ship (true angle = angle -1)
      angle := 1
      oldangle := 0
      firsttime := 1
      livesleft := 5
      livesdone := 0

      starsdone := 0
      if tapped = 1 then gamestart := 0
      tapped := 0
      score := 0
      oldscore := -1
		
      #kill any straggling asteroids or blasts
      every blasts[1 to MAXBLASTS].flag := 0
      every roids[1 to MAXROIDS].active := 0
   end

   method handle_event(e)
      local pqz
      if tapped = 1 then {
	 tapped := 0
	 reset_everything()
	 drawstars()
         }
      if firsttime = 1 & starsdone = 1 then {
	 firsttime := 0
         }	
      if gamestart = 1 then {
	 case e of {
	    " ": {
	       #space bar, same as left click
		if shiphit = 0 then {
		    redrawship := 5
		    eraseblasts()
		    eraseship()
		    initblast(x1, y1, angle - 1)
		    eraseblasts()
		    drawship(x1, y1, angle)
		    }
	        }
	    "d" | "D" : {
	       Bg("black")
	       Fg("white")
	       GotoRC(10, 1)
	       WWrite(cwin, "                 ")
	       GotoRC(10, 1)
	       WWrite(cwin, "Here: ", num_ships, " ", num_level,
		      " ", num_rotation)
	       }
	    "q" | "Q": {
	       exit()
	       }
	    Key_Left:	 {
	       angle -:= 5
	       if(angle <= 0) then angle +:= 360
	       left_pressed := 1
	       }
	    Key_Right: {
	       angle +:= 5
	       if(angle > 360) then angle -:= 360
	       right_pressed := 1
	       }
	    -(Key_Left)-128: {
	       left_pressed := &null
	       }
	    -(Key_Right)-128: {
	       right_pressed := &null
	       }
	    -(Key_Up)-128: {
	       up_pressed := &null
	       }
	    -(Key_Down)-128: {
	       down_pressed := &null
	       }
	    Key_Up: {
	       speedx +:= lookupc[angle] * SPEEDINC
	       speedy +:= lookups[angle] * SPEEDINC
	       if speedx > MAXSPEED then speedx := MAXSPEED
	       if speedx < (NEGMAXSPEED) then speedx := NEGMAXSPEED
	       if speedy > MAXSPEED then speedy := MAXSPEED
	       if speedy < (NEGMAXSPEED) then speedy := NEGMAXSPEED
	       up_pressed := 1
	       }
	    Key_Down:	 	{
	       speedx -:= lookupc[angle] * SPEEDINC
	       speedy -:= lookups[angle] * SPEEDINC
	       if(speedx > MAXSPEED) then speedx := MAXSPEED
	       if(speedx < (NEGMAXSPEED)) then speedx := NEGMAXSPEED
	       if(speedy > MAXSPEED) then speedy := MAXSPEED
	       if(speedy < (NEGMAXSPEED)) then speedy := NEGMAXSPEED
	       down_pressed := 1
	       }
	    }
         }
   end

   method idle_func()
      local px, py, maxspeed, dist
      local doskip, intdist, delayed, starclones, temp

      # don't start until they say New Game
      if not (\gamestart=1) then fail

      delayed := 0
      #	    redrawship := 1

      #everything is drawn in white, may change later on
      Fg("white")

      if livesdone=0 then {
	 every pqz := 1 to livesleft do {
	    drawship2((((pqz-1)*34)+18) , 42)
	    }
	 }

      #game loop
      while *Pending() = 0 do {

	 if score ~= oldscore then {
	    oldscore := score
	    Bg("black")			
	    GotoRC(4, 30)
	    WWrite(cwin, score)
	    }
	 if (shipx~= x1 | shipy ~= y1 | oldangle ~= angle) & (shiphit = 0)then{
	    #we're redrawing it here, no need to elsewhere
	     redrawship := 0
	     oldangle := angle	
	     #finally, draw the ship
	     eraseblasts()
	     drawship(x1, y1, angle-1)
	     drawblasts()
	     WDelay(DELAY_TIME)
	     #already did delay, don't do it again
	     delayed := 1
	     }
	 else if shiphit > 0 then { 
	     redrawship := doexplodeship()
	     x1 := MAXWIDTH / 2
	     y1 := MAXHEIGHT / 2
	     }
	 x1 +:= speedx
	 y1 +:= speedy

	 if(x1 > MAXWIDTH - 20) then x1 := 20
	 if(x1 < 20) then x1 := MAXWIDTH - 20
	 if(y1 > MAXHEIGHT - 20) then y1 := 20 + VOFFSET
	 if(y1 < (20 + VOFFSET)) then y1 := MAXHEIGHT - 20

	 #randomly put in a new asteroid, up to the max
	 #may change rules for this based on a kind of level system
	 if currroids < MAXROIDS then {
	    if ?1000 > ROIDPROBABILITY then {
	       eraseblasts()
	       #               eraseship()
	       eraseroids()
	       initroid()
	       eraseroids()
	       #                       drawship(x1, y1, angle-1)
	       drawblasts()
	       }
            }
	 #thinking I ought to split these boys up, would save on if statements
	 if currblast > 0 | currroids > 0 then {
	    if currblast > 0 then eraseblasts()
	    if currroids > 0 then eraseroids()
	    if redrawship > 0 then eraseship()
	    if currroids > 0 then animroids()
	    if currblast > 0 then animblasts()
	    if redrawship > 0 then {
	       drawship(x1, y1, angle-1)
	       redrawship -:= 1
               }
	    if currroids > 0 then drawroids()
	    if currblast > 0 then drawblasts()
	    if delayed = 0 then WDelay(DELAY_TIME)
	    else delayed := 0
            }
	if \left_pressed then
	   handle_event(Key_Left)
	if \right_pressed then
	   handle_event(Key_Right)
	if \up_pressed then
	   handle_event(Key_Up)
	if \down_pressed then
	   handle_event(Key_Down)
        }
      #aha! they did something!
   end

Strategy games

What is strategy? What is tactics?

strategy

a plan. how to string the battles together in order to win the war. example: we will win the war by blockading the enemy's ports

tactics

techniques for using weapons/units in combination to win a battle. example: we will win the battle by convincing the enemy that we are far more numerous and confusing them.

Real Time vs. Turn-based

Real-time Strategy Games are usually a misnomer. The actions of players of real-time strategy games are usually tactics.

Example Old-School Tabletop Turn-Based Strategy Games

• Empire (ascii art) (description)
• Ogre and G.E.V. (microgames)
• Civilization (there was a boardgame prior to Sid Meier's PC games, but Sid Meier's Civilization is quite a bit different)
• SPI and Avalon Hill Games (detailed simulations of the most famous battles in history, Civil War, WW II, etc.)

Example Turn-Based Strategy Computer Games

• battle for wesnoth
• ruse -- wwii -- scales from individual soldiers to miles-and-miles
• age of empires -- balancing, extensible unit behavior
• stronghold -- defensive, plan to withstand the onslaught
• simcity -- non-combat
• sins of a solar empire

Example Real-Time Strategy Games

• Warcraft (not World-of, just Warcraft)
• Dune II, Command and Conquer
• Dozens of me-too games, including many great ones

Writing your own Ogre game

class Hex(row, col,    # integer row and column #, used in x,y calculations
          terraintype, # for ogre: "normal" and "impassable"
          units,       # list of (0-or-1, or 0-or-more, check rules) unit objs
          exits)       # list of 6 adjacent hexes
   method draw()
      # draw the terrain
      if terraintype == "impassable" then {
         Pattern()
         }
      FillPolygon( vertices... )

      # draw the edges
      DrawLine(vertices...)
      every i := 1 to 6 do {
         if exits[i] === &null then {
            # draw the impassable edge
            }
         }

      # draw the units
      if *units > 0 then # draw what is on the top of the stack
         units[1].draw()
      if *units > 1 then # draw "multi-unit stack" decoration
   end
end

Guest Discussion with Dr. Ian Chambers

Recommended comprehensive pirate sites:

• Rob Ossian's Pirate's Cove
• Cindy Vallar's Pirates and Privateers

Dr. Chambers' recommended pirates and scenarios:

Blackbeard

swam headless around the whole ship. boss battles were not invented by videogame designers in the 1980's

Julius Caesar

ultimate revenge scenario: sought out and destroyed his pirate captors

Henry Morgan

note the cows and nuns as weapons

Treasure Island

multiple locations, long-voyage-plot, hunt for buried treasure, the works

Open discussion / brainstorming

Rabin of the Day

• Chapter 3.5, Debugging Games.

Ogre Show and Tell

Why Ogre?

The Metagaming Microgames are nearly perfect examples of small-scale games that could be fully implemented in not many lines of code.

sequel G.E.V.

adds many near-future unit types, terrain effects, and scenarios

Other microgames

hand-to-hand combat games Melee and Wizard were precursors to GURPS

Designed by Steve Jackson

Later founded Steve Jackson Games and the famous Munchkin card games.

Turn-based

Focus on the simulation mechanics, not twitch skills; would be fun challenge to carefully adapt to real-time.

All About Tactics

Microgames take only a few minutes to play, don't involve strategy much. Hard to come up with a "small scale strategy game" that's really strategy.

Ogre: Now What?

Unit class

class representation for Units, including Ogres. Let's design it now.

user input

translation of mouse actions on the map into events on (row,col) hex locations.

execution of game rules

turn sequence; movement and combat

AI

The game can be two-player with no AI, but the most fun scenario is where the computer plays the Ogre and you the puny human plays the humans trying to survive. Alternately, you could be the Ogre, and let the computer try to survive.

Double Header?

Grading Update

Next Virtual Environment

Rabin of the Day

• Chapter 3.6, Game Architecture.

Checkers

Minimax Algorithm

Given a board position P we wish to calculate our best possible move. There is a tree of board positions which allows us to evaluate all possible moves*.

From the current position we select the next move as the child whose board position is best (maximizing our position). But our evaluation of board positions considers further moves (deeper "look ahead") as much as CPU allows. We can reasonably assume our adversary will make their best possible move (minimizing our position). Our best position, short of forcing a win, will be whatever gives the opponent the least opportunity.

procedure minimax(node, depth)
    if gameover(node) | (depth = 0) then {
        return evaluate(node)
	}
    else {
        α := -&infinity;
        every child := possiblemoves(node) do {
            α <:= -minimax(child, depth-1)
	    }
        return α
end

Good: allows perfect play

Bad: may require infinite compute resources

Alpha-beta pruning

Lecture 13. Minimax, Strategy Games

HW#2 Status Update

Comment on Minecraft vs. SecondLife

• Some students requested Minecraft instead of SL, claiming it is a multiuser virtual environment already.
• Minecraft is popular but it is not free.
• I think it would be good to be familiar with both MC and SL in this class
• Point of next virtual environment study is world-building.
• Compared to LOTRO, both MC and SL have the fatal flaw of not having a coherent narrative other than "build stuff".

Rabin

Tic-Tac-Toe and the Minimax Algorithm

L := [ [" ", " ", " "],
       [" ", " ", " "],
       [" ", " ", " "] ]

L := [ [1,1,1], [1,1,1], [1,1,1] ]

We need an evaluation function. By definition it is a heuristic function, although with simple games and extreme cases it may be that the heuristic can be proved to produce optimal results.

procedure evaluate(L, player)
   if player=="x" then { player := 2; enemy := 3 }
   else { player := 3; enemy := 2 }

   # absolute results
   # 1000 if there exists a 3-in-a-row
   # -1000 if there exists an enemy 3-in-a-row
   if numNinaRow(L, player, 3)>0 then return 1000
   if numNinaRow(L, enemy, 3)>0 then return -1000

   # heuristic opinions
   sum := 0
   # + 100  for each (unblocked) 2-in-a-row
   # - 100  for each enemy (unblocked) 2-in-a-row
   sum +:= 100 * numNinaRow(L, player, 2)
   sum -:= 100 * numNinaRow(L, enemy, 2)
   # + 10   if we hold the center square
   # - 10   if we hold the center square
   if player = L[2,2] then sum +:= 10
   if enemy = L[2,2] then sum -:= 10
   # + 2    for each corner square
   # - 2    for each enemy corner square
   if player = L[1,1] then sum +:= 2
   if player = L[1,3] then sum +:= 2
   if player = L[3,1] then sum +:= 2
   if player = L[3,3] then sum +:= 2
   if enemy = L[1,1] then sum -:= 2
   if enemy = L[1,3] then sum -:= 2
   if enemy = L[3,1] then sum -:= 2
   if enemy = L[3,3] then sum -:= 2
   return sum
end

procedure numNinaRow(L, player, n)
   sum := 0
   n := player ^ n
   every i := 1 to 3 do {
      if L[1,i] * L[2,i] * L[3,i] = n then sum +:= 1
      if L[i,1] * L[i,2] * L[i,3] = n then sum +:= 1
      }
   if L[1,1] * L[2,2] * L[3,3] = n then sum +:= 1
   if L[1,3] * L[2,2] * L[3,1] = n then sum +:= 1
   return sum
end   

Extending Minimax to RTS or MMO

• Minimax is a centralized intelligence
• Different possible ways to develop concurrent plans for all units
• Sauron-style -- a concurrent minimax could prioritize all units and calculate deeper for important ones, and calculate others with knowledge of what the other units are doing, especially neighbors and important units
• A possibly-more-realistic concurrent minimax might let each unit calculate what it is doing independently.
• Centralized management could be applied via dynamically changing each unit's evaluation function

Comments on Monsters and NPC's

• Monsters and non-player characters need some kind of execution model.
• Moving past "Cellular Automata" such as "Life"...
• Many games use "good ole" finite automata (wander mode, sleep mode, fight mode, flight mode...)
• Good execution models need to (look and) "feel" intelligent.
• You can certainly apply a variant of a minimax algorithm, especially if a central intelligence controlling many units (Sauron)
• Is the goal in a game to appear human-like in intelligence?
• Behavior Trees are a model with alleged advantages over finite automata
• BDI (belief-desire-intention) is a popular human-like AI model.

Behavior Trees

• Build a tree data structure to organize complex unit behavior rules.
• Different node types for prioritized, sequenced, conditional and concurrent/alternating behaviors

BDI

• Michael Bratman
• desire+"commitment"=intention
• selection of plans from a "plan library"
• balance (re)selection time vs. execution time
• execute the current plan until completion or commitment timeout
• does not include how to create plans

How are your HW#3's doing?

• I received one turnin last night
• I suspect most folks are still working furiously on their HW's
• I haven't received a lot of requests for appointments or questions by e-mail.
• You need to get something reasonable working and turned in soon

Where we are at in the course

Week 4 and 5 Notes

here and here

No one volunteered for taking this week

any volunteers? A small number of points will be associated with your note taking, so be sure to sign up (except Idaho Falls folks)

schedule says last week we should have hit game math & physics

we didn't, we are a bit behind

and this week we should be talking graphics and virtual environments.

we will

HW#2

I did more grading over the weekend, but my apologies: given a choice between preparing for class or grading, I prepare for class

Strategy Game code (ogre) example

The Ogre program is available at http://www2.cs.uidaho.edu/~jeffery/courses/428/ogre-v0/ and as I said before, it is a semi-playable useful example of computerizing a manual strategy game, but needs a lot of refinement.

Second Life

Please work your way through the tutorial island and head to Dr. J's place. Can we do a session in Second Life by tomorrow night? Secondlife.com handles user account creation; a tiny link at the bottom says "Downloads". Last I looked, It offers Windows, OSX, and Linux binaries. I am going to assume that we have no problems with you getting a working SecondLife client. If you do have a problem, let me know ASAP. My SL user name is Jeffery Clinton.

Unicon

Unicon has already been updated once this semester and another update is forthcoming.

Rabin of the Day

Chapter 4.1, Mathematical Concepts.

This feels a lot like CS 324 review material, but for most of you there are one or more elements that are new or need brushing up or dusting off.

Parallel Concerns, Moving into Virtual Environments

• learn enough Unicon to do the VE assignments
• learn about 3D programming
• learn about 3D modeling
• start assembling some "pirate assets"
• try out SecondLife's (and/or MineCraft's) content creation
• introduce CVE

Raw Data

There is one other kind of raw data I'd like you to collect: yourselves. I want to push beyond the crude avatars I've used previously, and model ourselves in crude, low-polygon textured glory.

On Coordinate Systems

To anyone who gets confused about a positive axis running from right to left or from top to bottom instead of what you were expecting: this just means that your perspective is turned around from those used by the world coordinates. If your character rotates 180 degrees appropriately, suddenly positive values go the opposite direction from before and what was right to left is the more familiar left to right. The point: world coordinates are different from your personal eyeball coordinate system, don't confuse them.

A Common Coordinate System

measure its x and z using FHN,
• measure its y (how?)
• identify its exits (doors and openings) and for each exit,
  • its connecting room
  • its x,y,z, height, and plane
• collect textures for floor, walls, ceilings, doors, decorations
• identify major obstacles (essential virtual objects in the room)

Another Sample Room

Room {
name SH 167
x 29.2
y 0
z 0.2
w 6
h 3.05
l 3.7
floor Wall {
texture floor2.gif
coords [29.2,0,0.2, 29.2,0,3.9, 35.2,0,3.9, 35.2,0,0.2]
}
obstacles [
   Box { # column
      Wall {coords [34.3,0,0.2, 34.3,3.05,0.2, 34.3,3.05,0.6, 34.3,0,0.6]}
      Wall {coords [34.3,0,0.6, 34.0,0,0.6, 34.0,3.05,0.6, 34.3,3.05,0.6]}
      Wall {coords [34.0,0,0.6, 34.0,3.05,0.6, 34.0,3.05,0.2, 34.0,0,0.2]}
      }
   Box { # window sill
      Wall {coords [29.2,0,0.22, 29.2,1.0,0.22, 35.2,1.0,0.22, 35.2,0,0.22]}
      Wall {coords [29.2,1,0.22, 29.2,1.0,0.2,  35.2,1.0,0.2, 35.2,1,0.22]}
      }
   Chair {
          coords [31.2,0,1.4]
   	  position 0
	  color red
	  type office
          movable true         
         }
   Table {
         coords [31.4,0,2.4]
   	 position 180
	 color very dark brown
	 type  office
       }
   ]
decorations [
   Wall { # please window
      texture wall2.gif
      coords [29.2,1.0,0.22, 29.2,3.2,0.22, 35.2,3.2,0.22, 35.2,1.0,0.22]
      }
   Wall { # whiteboard
      texture whiteboard.gif
      coords [29.3,1.0,3.7, 29.3,2.5,3.7, 29.3,2.5,0.4, 29.3,1.0,0.4]
      }
   Windowblinds {
           coords [29.2,1.5,0.6]
           angle 90
           crod  blue
           cblinds  very dark purplish brown 
           height 3.05
           width  6
   }
]
}

HW#2 Update

HW#4: a short homework

Rabin: 3D Graphics

Chapter 5.1, Graphics. (backup).

a slight re-ordering; we will come back to Chapter 4.2, Collision Detection but 3D graphics comes first.

Lecture 16. Unicon 3D facilities; jeb demo

Where we are at

• Week 7 Notes
• As of 11:40am today, I have received HW#3's from 11 students, about 2/3rds of the class. If you haven't turned in a HW#3, I want a status report.
• Last time we spent the whole lecture on 3D fundamentals.
• Today we will do more concrete examples, and we will just push Rabin to the back burner since he used the whole class last Thursday.
• I would like to schedule a secondlife session this week. When would be best?
• On Thursday, there will be a take-home midterm exam posted.

Follow-on 3D Graphics in Unicon

• Grad students Jafar and Hani and myself have worked very hard to get out a new version of Unicon with various fixes and usability improvements for your viewing pleasure.
• Version 11.8 was a bugfix release, which had performance issues we fixed
• Version 11.9 (current) seems to work well on Win7 but we are looking at tweaking it (to 11.9.1 or whatever) to run better on XP if you need that.
• Version 12.0 is the Big New Thing we are in beta on, it adds threads and concurrency as a generalization of co-expressions.

History of 3D Graphics in Unicon

• OpenGL, Direct3D, Java3D, and often even higher level toolkits like OpenInventor have high learning curves, measured in months not days.
• For Unicon, we wanted Very High Level 3D, not just a "C/C++ binding".
• Design goals: resemble Unicon 2D facilities. Interoperate where feasible. Simplify compared with OpenGL (no new types. 20 functions instead of 250+).
• Undergraduate Math major Naomi Martinez developed 3D graphics in Unicon around 2003. Dr. J ported it to Windows the summer after Naomi did it on Linux. It has since been improved by several other students.
• Ended up with 16 new functions, 6 2D functions extended for 3D
• Current status: near-final. In need of further work on fonts, shaders, dynamic textures.
• Documentation: UTR9b; also summarized in the Unicon book.
• Class libraries: unicon's uni/3d subdirectory contains class libraries by Jafar Al Gharaibeh for doing things like using 3D models (Microsoft .x text format is our primary format).

Opening 3D Window

procedure main(av)
   &window := open("gl attributes", "gl", "canvas=hidden")
   write("glversion  : ", WAttrib("glversion"))
   write("glvendor   : ", WAttrib("glvendor"))
   write("glrenderer : ", WAttrib("glrenderer"))
end

Eye

Primitives

Transformation Stacks

• IdentityMatrix(), PushMatrix(), PopMatrix()
• Normal use: hierarchy of primitives with relative coordinate systems
• projection and modelview stacks, MatrixMode() switches

Lighting, Color, Materials

• OpenGL uses pretty generic/weak lighting model (Phong)
• Default lighting is generic, ambient
• Attributes light0-light7 are on or off
• Light values include diffuse, ambient, specular, and position
• Light syntax: "{diffuse,ambient,specular} colorname"
• My impression is that "diffuse" gives most simple control, and the effects of others is subtle.
• Example: WAttrib("light0=on, diffuse yellow; ambient gold") ...
• Standard X11 Colors are 48-bit (boo)
• Surface materials include diffuse, ambient, specular, and shininess components, or they can be textured, or material+texture blend
• Example materials:
  Fg("{diffuse,ambient,specular,emission} colorname")

Textures

• Attribute texmode can be on or off
• Example: WAttrib("texmode=on", "texture=map.gif"), WAttrib("texcoord=...")
• Also note: Texture(t) is more flexible than texture=... t can be a window
• Texture images have width, height that are powers of 2
• In Unicon, textures can be in-lined "image strings", filenames of image files .gif (.jpg, .png), other windows.
• Texture coordinates are set via attribute texcoord, function Texcoord().
• Either texcoord=auto or x1,y1,x2,y2,... are mapped to vertices of a subsequently called primitive such as FillPolygon().
• Texture coordinates > 1.0 imply repetitions of the image (tiling)
• Possible to blend textures and materials
• Possible (preliminary/unfinished) to "draw" directly on textures.

  w := open("win1","gl","bg=light blue","size=256,256")
  Fg(w, "emission pale grey")
  PushMatrix(w)
  Rotate(w, -5.0, 1.0, 0.0, 0.0)
  DrawCylinder(w, 0.0, 0.575, -2.0, 0.15, 0.05, 0.17)
  PopMatrix(w)  
  Fg(w, "diffuse grey; emission black")
  PushMatrix(w)
  Rotate(w, -5.0, 1.0, 0.0, 0.0)
  DrawCylinder(w, 0, 0, -2.5, 0.7, 0.035, 0.035)
  PopMatrix(w)
  DrawTorus(w, 0.0, -0.22 -2.5, 0.03, 0.06)
  DrawTorus(w, 0.0, 0.6, -2.5, 0.05, 0.03)

  w2 := open("win2.icn","gl","bg=black","size=400,400")
  WAttrib(w2, "texmode=on")
  Texture(w2, w)
  Fg(w2, "diffuse purple; ambient blue")
  DrawCylinder(w2, 0, 0, -3.5, 1.2, 0.7, 0.7)

3D Selection

The jeb demos

• Unicon3D
• 3D modeling
• the internals of the CVE virtual environment

• jeb1 and jeb1.zip
• jeb2 and jeb2.zip
• jeb3 and jeb3.zip

Our modest goals: understand some Unicon language features used, consider how to Piraticize these demos, contemplate writing equivalent (or better) demos in your preferred language(s), planning to extend to networking soon.

Diving into Jeb1

jeb1: jeb1.icn model.u
	unicon jeb1 model.u

model.u: model.icn
	unicon -c model

jeb1.zip: jeb1.icn model.icn
	zip jeb1.zip jeb1.icn model.icn *.gif *.dat makefile README

jeb1.icn

• ~500 lines. If you want to reimplement in your preferred language, go for it. Down the road this has to include TCP networking.
• IVIB-generated GUI front end
• Embeds a 3D subwindow in a larger 2D window
• class Subwindow3D is a bit of a hack but shows technique
• Dispatch message loop overridden for subwin and net
• include-in-example modelfile parser should be outsourced.

A Walk Through a Smattering of Jeb1

    WAttrib("texmode=on")

Assigning a value to a variable uses := in Unicon. Most of the rest of the numeric operators and computation is the same as in any programming language. In 3D graphics, a lot of real numbers are used. In the jeb1 demo, the user controls a moving camera, which has an (x,y,z) location, an (x,y,z) vector describing where they are looking, relative to their current position, and camera angles up or down. Initial values of posx and posy are "in the middle of the first room in the model". The rooms have min and max values for x,y, and z so:

	       posx := (r.minx + r.maxx) / 2
	       posy := r.miny + 1.9
	       posz := (r.minz + r.maxz) / 2
	       lookx := posx; looky := posy -0.15; lookz := 0.0

Unicon has a "list" data type for storing an ordered collection of items. There is a global variable named Room which holds such a list, a list of Room() objects. We will discuss Room() objects in a bit. This is how the list of rooms is created, with 0 elements:

    Rooms := [ ]

The code that actually reads a model file and creates Room() objects and puts them on the Rooms list is procedure make_model(). We defer the actual parsing discussion to later or elsewhere.

procedure make_model(corridor)
local fin, s, r
   fin := open(modelfile) | stop("can't open model.dat")
   while s := readlin(fin) do s ? {
       if ="#" then next
       else if ="Room" then {
	   r := parseroom(s, fin)
	   put(world.Rooms, r)
	   world.RoomsTable[r.name] := r
	   if /posx then {
	       # ... no posx defined, calculate posx/posy per earlier code
	   }
       }
       else if ="Door" then parsedoor(s,fin)
       else if ="Opening" then parseopening(s,fin)
       # else: we didn't know what to do with it, maybe its an error!
   }
   close(fin)
end

The following line steps through all the elements of the Rooms list, and tells each Room() to draw itself. The exclamation point is an operator that generates each element from the list if the surrounding expression requires it. The "every" control structure requires every result the expression can produce. The .render() calls a method render() on an object (in this case, on each object in turn as it is produced by !). Note that our CVE will probably want to get smart about only drawing those rooms that are "visible", in order to scale performance.

    every (!Rooms).render()

Aspects of the .dat file format

Obstacles

Answer: in HW4 such a thing might be omitted, but you might get around to including the column as an obstacle (a virtual Box) in your .dat file. The obstacles section is also where things like bookshelves and tables might go.

obstacles [
   Box { # column
      Wall {coords [34.3,0,0.2, 34.3,3.05,0.2, 34.3,3.05,0.6, 34.3,0,0.6]}
      Wall {coords [34.3,0,0.6, 34.0,0,0.6, 34.0,3.05,0.6, 34.3,3.05,0.6]}
      Wall {coords [34.0,0,0.6, 34.0,3.05,0.6, 34.0,3.05,0.2, 34.0,0,0.2]}
      }
]

Ceilings?

The parser is a handwritten in a vaguely recursive descent style; at syntax levels where many fields can be read, it builds a table (so order does not matter) from which we populate an object's fields. So the table t's fields correspond to what the file had in it, and the .coords here is the list of vertices which the object in the model wants.

   if \ (t["ceiling"]) then {
      t["ceiling"].coords := [t["x"],t["y"]+t["h"],t["z"],
                t["x"],t["y"]+t["h"],t["z"]+t["l"],
                t["x"]+t["w"],t["y"]+t["h"],t["z"]+t["l"],
                t["x"]+t["w"],t["y"]+t["h"],t["z"]]
      t["ceiling"].set_plane()
      r.ceiling := t["ceiling"]
      }

ceiling Wall {
texture jeb230calendar.gif
}

Event Handling

   repeat {
      if *Pending() = 0 then { # continue in current direction, if any }
      else {
         case ev := Event() of {
	    Key_Up:    cam_move(xdelta := 0.05)		# Move Foward
            ... other keys
            }
         }

Events may be strings (for keyboard characters), but most are small negative integer codes, with symbolic names such as Key_Up defined in keysyms.icn.

$include "keysyms.icn"

   method message_loop(r)
   local L, dialogwins, x
      connections := []
      dialogwins := set()
      every insert(dialogwins, (!dialogs).win)
      every put(connections, !dialogwins | !subwins | !nets)
      while \r.is_open do {
	 if x := select(connections,1)[1] then {
            if member(subwins, x) then {
	       &window := x
	       do_cve_event()
	       }
            else if member(dialogwins, x) then do_event()
            else if member(nets, x) then do_net(x)
	    else write("unknown selector ", image(x))

	    # do at least one step per select() for smoother animation
	    do_nullstep()
	    }
         else do_validate() | do_ticker() | do_nullstep() | delay(idle_sleep)
	 }
   end

   method do_cve_event()
   local ev, dor, dist, closest_door, closest_dist, L := Pending()
      case ev := Event() of {
	 Key_Up: {
	    xdelta := 0.05
	    while L[1]===Key_Up_Release & L[4]===Key_Up do {
	       Event(); Event(); xdelta +:= 0.05
	       }
	    cam_move(xdelta)		# Move Foward
	    }
	 Key_Down: {
	    xdelta := -0.05
	    while L[1]===Key_Down_Release & L[4]===Key_Down do {
	       Event(); Event(); xdelta -:= 0.05
	       }
	    cam_move(xdelta)	# Move Backward
	    }
	 Key_Left: {
	    ydelta := -0.05
	    while L[1]===Key_Left_Release & L[4]===Key_Left do {
	       Event(); Event(); ydelta -:= 0.05
	       }
	    cam_orient_yaxis(ydelta) # Turn Left
	    }
	 Key_Right: {
	    ydelta := 0.05
	    while L[1]=== Key_Right_Release & L[4] === Key_Right do {
	       Event(); Event(); ydelta +:= 0.05
	       }
	    cam_orient_yaxis(ydelta)	 # Turn_Right
	    }
	 "w":       looky +:= (lookdelta := 0.05)  #Look Up
	 "s":       looky +:= (lookdelta := -0.05) #Look Down
	 "q": exit(0)
	 "d": {
	    closest_door := &null
	    closest_dist := &null
	    every (dor := !(world.curr_room.exits)) do {
	       if not find("Door", type(dor)) then next
	       dist := sqrt((posx-dor.x)^2+(posz-dor.z)^2)
	       if /closest_door | (dist < closest_dist) then {
		  closest_door := dor; closest_dist := dist
	          }
	       }
	    if \closest_door then {
	       if \ (closest_door.delt) === 0 then {
	          closest_door.start_opening()
	          }
	       else closest_door.done_opening()
	       closest_door.delta()
	       }
	    }
	 -166 | -168 | (-(Key_Up|Key_Down) - 128) :    xdelta := 0
	 -165 | -167 | (-(Key_Left|Key_Right) - 128) : ydelta := 0
	 -215 | -211 : 	lookdelta := 0
        }

      Eye(posx,posy,posz,lookx,looky,lookz)

   end

The Line Between jeb1.icn and model.icn

model.icn

Wall() is the simplest class here, it is just a textured polygon, holding a texture value and a list of x,y,z coordinates, and providing a method render(). Every object in the CVE's model will provide a method render().

class Wall(texture, coords)
   method render()
      if current_texture ~=== texture then {
         WAttrib("texture="||texture, "texcoord=0,0,0,1,1,1,1,0")
         current_texture := texture
         }
      (FillPolygon ! coords) |  write("FillPolygon fails")
   end
initially(t, c[])
  texture := t
  coords := c
end

Class Box() is more interesting, it is a rectangular area with walls that one cannot walk through, and a bounding box for collision detection. Doors, openings, and other exceptions are special-cased by subclassing and overriding default behavior. Rectangular areas are singled out because they are common and have easy collision detection; when a wall goes from floor to ceiling, collision detection reduces to a 2D problem.

Box() has methods:

• mkwall() (to make walls)
• render() (to draw)
• disallows(x,z) to assist in collision detection

Class Door() is not just a graphical object, it is a connection between (2) rooms, which can be open (1.0) or closed(0.0) or in between. It supports methods:

• render() to draw the door
• set_openness(o) to specify how open (ajar) the door is
• add_room(r) to attach a room to the door
• other(room) to compute the other room
• allows(px,pz) to check whether the door is open enough to walk through.
• start_opening(), delta(), and done_opening() when the user activates the door, as the door is opening or closing, and when it finishes. The direction toggles each time, between opening and closing.

The full code of jeb1.icn

import gui
$include "guih.icn"

class Untitled : Dialog(chat_input, chat_output, text_field_1, subwin)
   method component_setup()
      self.setup()
   end

   method end_dialog()
   end

   method init_dialog()
   end

   method on_exit(ev)
      write("goodbye")
      exit(0)
   end

   method on_br(ev)
   end

   method on_kp(ev)
   end

   method on_mr(ev)
   end

   method on_subwin(ev)
      write("subwin")
   end

   method on_about(ev)
   local sav
      sav := &window
      &window  := &null
      Notice("jeb1 - a 3D demo by Jeffery")
      &window := sav
   end

   method on_chat(ev)
      chat_output.set_contents(put(chat_output.get_contents(), chat_input.get_contents()))
      chat_output.set_selections([*(chat_output.get_contents())])
      chat_input.set_contents("")
   end

   method setup()
      local exit_menu_item, image_1, menu_1, menu_2, menu_bar_1, overlay_item_1, overlay_set_1, text_menu_item_2
      self.set_attribs("size=800,750", "bg=light gray", "label=jeb1 demo")
      menu_bar_1 := MenuBar()
      menu_bar_1.set_pos("0", "0")
      menu_bar_1.set_attribs("bg=very light green", "font=serif,bold,16")
      menu_1 := Menu()
      menu_1.set_label("File")
      exit_menu_item := TextMenuItem()
      exit_menu_item.set_label("Exit")
      exit_menu_item.connect(self, "on_exit", ACTION_EVENT)
      menu_1.add(exit_menu_item)
      menu_bar_1.add(menu_1)
      menu_2 := Menu()
      menu_2.set_label("Help")
      text_menu_item_2 := TextMenuItem()
      text_menu_item_2.set_label("About")
      text_menu_item_2.connect(self, "on_about", ACTION_EVENT)
      menu_2.add(text_menu_item_2)
      menu_bar_1.add(menu_2)
      self.add(menu_bar_1)
      overlay_set_1 := OverlaySet()
      overlay_set_1.set_pos(6, 192)
      overlay_set_1.set_size(780, 558)
      overlay_item_1 := OverlayItem()
      overlay_set_1.add(overlay_item_1)
      overlay_set_1.set_which_one(overlay_item_1)
      self.add(overlay_set_1)
      subwin := Subwindow3D()
      subwin.set_pos(14, 195)
      subwin.set_size("767", "551")
      subwin.connect(self, "on_subwin", ACTION_EVENT)
      subwin.connect(self, "on_br", BUTTON_RELEASE_EVENT)
      subwin.connect(self, "on_mr", MOUSE_RELEASE_EVENT)
      subwin.connect(self, "on_kp", KEY_PRESS_EVENT)
      self.add(subwin)
      chat_input := TextField()
      chat_input.set_pos("12", "162")
      chat_input.set_size("769", "25")
      chat_input.set_draw_border()
      chat_input.set_attribs("bg=very light green")
      chat_input.connect(self, "on_chat", ACTION_EVENT)
      chat_input.set_contents("")
      self.add(chat_input)
      chat_output := TextList()
      chat_output.set_pos("10", "29")
      chat_output.set_size("669", "127")
      chat_output.set_draw_border()
      chat_output.set_attribs("bg=very pale whitish yellow")
      chat_output.set_contents([""])
      self.add(chat_output)
      image_1 := Image()
      image_1.set_pos("686", "31")
      image_1.set_size("106", "120")
      image_1.set_filename("nmsulogo.gif")
      image_1.set_internal_alignment("c", "c")
      image_1.set_scale_up()
      self.add(image_1)
   end

   initially
      self.Dialog.initially()
end

#
# N3Dispatcher is a custom dispatcher.  Currently it knows about 3D
# subwindows but we will extend it for networked 3D applications.
#
class N3Dispatcher : Dispatcher(subwins, nets, connections)
   method add_subwin(sw)
      insert(subwins, sw)
   end
   method do_net(x)
      write("do net ", image(x))
   end

   method do_nullstep()
   local moved, dor

   thistimeofday := gettimeofday()
   thistimeofday := thistimeofday.sec * 1000 + thistimeofday.usec / 1000
   if (delta := thistimeofday - \lasttimeofday) < 17 then {
      delay(17 - delta)
      }
   lasttimeofday := thistimeofday

      if xdelta ~= 0 then {
	 cam_move(xdelta)
	 moved := 1
	 }
      if ydelta ~= 0 then {
	 cam_orient_yaxis(ydelta)
	 moved := 1
	 }
      if lookdelta ~= 0 then {
	 looky +:= lookdelta; moved := 1
	 }
      every (\((dor := !(world.curr_room.exits)).delt)) ~=== 0 do {
	 if dor.delta() then moved := 1
         else dor.done_opening()
	 }
      if \moved then {
	 Eye(posx,posy,posz,lookx,looky,lookz)
         return
	 }
   end

method cam_move(dir)
local deltax := dir * cam_lx, deltaz := dir * cam_lz

   if world.curr_room.disallows(posx+deltax,posz+deltaz) then {
      deltax := 0
      if world.curr_room.disallows(posx+deltax,posz+deltaz) then {
	 deltaz := 0; deltax := dir*cam_lx
	 if world.curr_room.disallows(posx+deltax,posz+deltaz) then {
	    fail
	    }
	 }
      }

   #calculate new position
   posx +:= deltax
   posz +:= deltaz

   #update look at spot
   lookx := posx + cam_lx
   lookz := posz + cam_lz
end

#
# Orient the camera
#
method cam_orient_yaxis(turn)

   #update camera angle
   cam_angle +:= turn

   if abs(cam_angle) > 2 * &pi then
      cam_angle := 0.0

   cam_lx := sin(cam_angle)
   cam_lz := -cos(cam_angle)

   lookx := posx + cam_lx
   lookz := posz + cam_lz
end

   global lasttimeofday
   #
   # Execute one event worth of motion and update the camera
   #
   method do_cve_event()
   local ev, dor, dist, closest_door, closest_dist, L := Pending()
      case ev := Event() of {
	 Key_Up: {
	    xdelta := 0.05
	    while L[1]===Key_Up_Release & L[4]===Key_Up do {
	       Event(); Event(); xdelta +:= 0.05
	       }
	    cam_move(xdelta)		# Move Foward
	    }
	 Key_Down: {
	    xdelta := -0.05
	    while L[1]===Key_Down_Release & L[4]===Key_Down do {
	       Event(); Event(); xdelta -:= 0.05
	       }
	    cam_move(xdelta)	# Move Backward
	    }
	 Key_Left: {
	    ydelta := -0.05
	    while L[1]===Key_Left_Release & L[4]===Key_Left do {
	       Event(); Event(); ydelta -:= 0.05
	       }
	    cam_orient_yaxis(ydelta) # Turn Left
	    }
	 Key_Right: {
	    ydelta := 0.05
	    while L[1]=== Key_Right_Release & L[4] === Key_Right do {
	       Event(); Event(); ydelta +:= 0.05
	       }
	    cam_orient_yaxis(ydelta)	 # Turn_Right
	    }
	 Key_PgUp |
	 "w":       looky +:= (lookdelta := 0.05)  #Look Up
	 Key_PgDn |
	 "s":       looky +:= (lookdelta := -0.05) #Look Down
	 "q": exit(0)
	 "d": {
	    closest_door := &null
	    closest_dist := &null
	    every (dor := !(world.curr_room.exits)) do {
	       if not find("Door", type(dor)) then next
	       dist := sqrt((posx-dor.x)^2+(posz-dor.z)^2)
	       if /closest_door | (dist < closest_dist) then {
		  closest_door := dor; closest_dist := dist
	          }
	       }
	    if \closest_door then {
	       if \ (closest_door.delt) === 0 then {
	          closest_door.start_opening()
	          }
	       else closest_door.done_opening()
	       closest_door.delta()
	       }
	    }
	 -166 | -168 | (-(Key_Up|Key_Down) - 128) :    xdelta := 0
	 -165 | -167 | (-(Key_Left|Key_Right) - 128) : ydelta := 0
	 -215 | -211 | (-(Key_PgUp|Key_PgDn)-128): 	lookdelta := 0
        }

      Eye(posx,posy,posz,lookx,looky,lookz)

   end

   method message_loop(r)
   local L, dialogwins, x
      connections := []
      dialogwins := set()
      every insert(dialogwins, (!dialogs).win)
      every put(connections, !dialogwins | !subwins | !nets)
      while \r.is_open do {
	 if x := select(connections,1)[1] then {
            if member(subwins, x) then {
	       &window := x
	       do_cve_event()
	       }
            else if member(dialogwins, x) then do_event()
            else if member(nets, x) then do_net(x)
	    else write("unknown selector ", image(x))

	    # do at least one step per select() for smoother animation
	    do_nullstep()
	    }
         else do_validate() | do_ticker() | do_nullstep() | delay(idle_sleep)
	 }
   end
initially
      subwins := set()
      nets := set()
      dialogs := set()
      tickers := set()
      idle_sleep_min := 10
      idle_sleep_max := 50
      compute_idle_sleep()
end

class Subwindow3D : Component ()
   method resize()
     compute_absolutes()
     # WAttrib(cwin, "size="||w||","||h)
   end
   method display()
   initial please(cwin)
    Refresh(cwin)
   end
   method init()
      if /self.parent then
         fatal("incorrect ancestry (parent null)")
      self.parent_dialog := self.parent.get_parent_dialog_reference()

      self.cwin := (Clone ! ([self.parent.get_cwin_reference(), "gl",
			      "size="||w_spec||","||h_spec,
			      "pos=14,195", "inputmask=mck"] |||
			     self.attribs)) | stop("can't open 3D win")
      self.cbwin := (Clone ! ([self.parent.get_cbwin_reference(), "gl",
			       "size="||w_spec||","||h_spec,
			       "pos=14,195"] |||
			      self.attribs))
      set_accepts_focus()
      dispatcher.add_subwin(self.cwin)
   end
end

# link "world"

global modelfile

procedure main(argv)
   local d
   modelfile := argv[1] | stop("uasge: jeb1 modelfile")
   world := FakeWorld()
   #
   # overwrite the system dispatcher with one that knows about subwindows
   #
   gui::dispatcher := N3Dispatcher()
   d := Untitled()
   d.show_modal()
end


link model
global world


procedure make_model(cooridoor)
local fin, s, r
   fin := open(modelfile) | stop("can't open ", image(modelfile))
   while s := readlin(fin) do s ? {
       if ="#" then next
       else if ="Room" then {
	   r := parseroom(s, fin)
	   put(world.Rooms, r)
	   world.RoomsTable[r.name] := r
	   if /posx then {
	       r.calc_boundbox()
	       posx := (r.minx + r.maxx) / 2
	       posy := r.miny + 1.9
	       posz := (r.minz + r.maxz) / 2
	       lookx := posx; looky := posy -0.15; lookz := 0.0
	   }
       }
       else if ="Door" then parsedoor(s,fin)
       else if ="Opening" then parseopening(s,fin)
#       else write("didn't know what to do with ", image(s))
   }
   close(fin)
end

#CONTROLS:
#up arrow - move foward
#down arrow - move backward
#left arrow - rotate camera left
#right arrow - rotate camera right
# ' w ' key - look up
# ' s ' key - look down
# ' d ' key - toggle door open/closed

#if you get lost in space (may happen once in a while)
#just restart the program

$include "keysyms.icn"

#GLOBAL variables
global posx, posy, posz           # current eye x,y,z position
global lookx, looky, lookz        # current look x position and so on
global cam_lx, cam_lz, cam_angle  # eye angles for orientation
global xdelta, ydelta, lookdelta

global Rooms

procedure please(d)
local r
    &window := d
    WAttrib("texmode=on")

    #initialize globals
#    posx := 32.0; posy := 1.9; posz := 2.0
#    lookx := 32.0; lookz := 0.0;    looky := 1.75
    cam_lx := cam_angle := 0.0; cam_lz := -1.0

    # render graphics
    make_model()
    every r := !world.Rooms do {
	if not r.disallows(posx, posz) then
	    world.curr_room := r
    }
    every (!world.Rooms).render(world)

   xdelta := ydelta := lookdelta := 0
   dispatcher.cam_move(0.01)
   Eye(posx,posy,posz,lookx,looky,lookz)
    # ready for event processing loop
end

# fakeworld - minimal nsh-world.icn substitute for demo

record fakeconnection(connID)

class FakeWorld(
	current_texture, d_wall_tex, connection, curr_room,
	d_ceil_tex, d_floor_tex, collide, Rooms, RoomsTable
	)
method find_texture(s)
    return s
end
initially
  Rooms := []
  RoomsTable := table()
  collide := 0.8
  connection := fakeconnection()
  d_floor_tex := "floor.gif"
  d_wall_tex := "walltest.gif"
  d_ceil_tex := d_wall_tex
end



### Ivib-v2 layout ##
#...blah blah machine-generated comments omitted...

model.icn

• Model.icn is ~1400 lines
• We can't go through it all, but we can skim it for ideas.
• A small class library for virtual objects.
• Consider logical vs. physical modeling again
• Graphics-only: model should just be a data structure
• Typical 3D artist: model=data structure (with optional animations)
• VE builder: model=code class. unlimited behavior
• But we really want model=data structure!
• Want our cake and eat it too.

model.icn The only part we had time to look at today was the top of class Room:

Class Room()

class Room : Box(floor, # "wall" under our feet
	   ceiling,     # "wall" over our heads
	   obstacles,	# list: things that stop movement
	   decorations, # list: things to look at
	   exits,	# x-y ways to leave room
	   name
	   )

   method disallows(x,z)
      if /minx then calc_boundbox() 

      # regular area is normally OK
      if minx+1.2 <= x <= maxx-1.2 & minz+1.2 <= z <= maxz-1.2 then {
         every o := !obstacles do
            if o.disallows(x,z) then return
         fail
         }
      # outside of regular area OK if an exit allows it
      every e := !exits do {
         if e.allows(x,z) then {
            if minx <= x <= maxx & minz <= z <= maxz then {
               # allow but don't change room yet
               }
            else {
               curr_room := e.other(self) # we moved to the other room
               }
            fail
            }
         }
      return
   end

   method render()
      every ex := !exits do ex.render()
      WAttrib("texmode=on")
      floor.render()
      ceiling.render()

      every (!walls).render()
      every (!obstacles).render()
      every (!decorations).render()
   end

   method add_door(d)
      put(exits, d)
      d.add_room(self)

      # figure out what wall this door is in, and tear a hole in it,
      # for example, find the wall the please door is in,
      # remove that wall, and replace them with three

    every w := !walls do {
       c := w.coords
       if c[1]=c[4]=c[7]=c[10] then {
          if d.x = c[1] then write("door is in xplane wall ", image(w))
          }
       else if c[3]=c[6]=c[9]=c[12] then {
          if abs(d.z - c[3]) < 0.08 then { # door is in a zplane wall
             # remove this wall
             while walls[1] ~=== w do put(walls,pop(walls))
             pop(walls)
             # replace it with three segments:
             # w = above, w2 = left, and w3 = right of door
             w2 := Wall ! ([w.texture] ||| w.coords)
             w3 := Wall ! ([w.texture] ||| w.coords)
             every i := 1 to *w.coords by 3 do {
                w.coords[i+1] <:= d.y+d.height
                w2.coords[i+1] >:= d.y+d.height
                w2.coords[i] >:= d.x
                w3.coords[i+1] >:= d.y+d.height
                w3.coords[i] <:= d.x + d.width
                }
            put(walls, w, w2, w3)
            return
            }
         }
       else { write("no plane; giving up"); fail }
       }
   end

   method add_obstacle(o)
      put(obstacles, o)
   end
   method add_decoration(d)
      put(decorations, d)
   end

Introduction to Second Life

• SecondLife source code page

Second Life is a non-game virtual environment. It is also a platform for building different kinds of virtual environment experiences. Many people are building amazing things in-world, and many are building amazing interfaces to external resources. Here are some interesting links.

• http://uk.youtube.com/watch?v=9hte2MJ54CA
• SecondLife Grid has a bunch of links for SecondLife developers. A "Developer" here might not be a software developer (programmer) it might be a virtual real estate developer, or virtual business developer.

Compared with game MMOs like Lord of the Rings Online or World of Warcraft, there is nothing to do, and everything to do. Instead of your character becoming skilled in pretend fishing, in SL you might yourself become skilled in creating virtual content, and getting paid for it.

Lecture 18.

Where We are At

• Take-Home Midterms Just Turned In -- will discuss Thursday
• Schedule says: we are a bit behind on the Rabin chapters
• Jeffery says: we are trying to bridge the gap between the JEB demo and the CVE program, an enormous gulf.
• Need to explore several major topic areas: 3D modeling and animation, networking for multi-user games, A/I...
• Really want to go beyond the CVE program in some of these areas.
• Time for a new homework assignment, HW#5.

A "missing link"

FPS's

• Wolfenstein 3D
  
• Doom
  
• Quake (source)

Another option is to search for higher (-level) ground, such as filling in some of the gaps between the ~2.5K LOC jeb demo and the FPS genre. The main differences between wandering around the halls of a CS department (the JEB demo) and Wolfenstein 3D or Doom are:

animated 3D enemy characters

3D models, simple A/I

simple combat system

health meter, attack and damage animations

a very few virtual objects

weapons, armor, health kits

3D Modeling, Part I

A 3D Model, for the purposes of this class

A data structure (with an external representation -- a file format) capable of representing an arbitrary-shaped, generally solid object and that object's range of motions.

Start with: Polygon Mesh and Texture(s)

Add: bone structure, motion API

(strangely?) OpenGL does not have built-in 3D models.

If you dig, you find that SGI did a sweet toolkit atop OpenGL called OpenInventor, but that never became ubiquitous as OpenGL. OpenInventor influenced the design of VRML, which influenced the design of X3D.

No universal standard for 3D modeling that I know of.

Suggestions welcome

3D Model File Format Requirements

"open". public. platform neutral. easily parsed. preferably human readable. "adequate" performance.

scripted animation versus program control?

Sort of a question of how much manual artistry can we afford. Artists make better-looking animation, but are too expensive. Ideal would be: a set of general parametric or programmable animations.

In this class we will discuss two 3D model formats: S3D and .X

The S3D (simple 3D)

S3D File Format Overview

You really need to see some sample S3D files in order to get a feel for the beauty of the S3D file format. s3dparse.icn, and S3D files themselves, may have various usually-nonfatal "bugs". There was even a bug in the S3D file format document.

We also took a look at the desperate situation vis a vis creating 3D models (a job performed by experts with much training) and our need to build such models for our games and virtual environments. Let us continue from there.

A Grim S3D Example (Part 1)

• What is the absolute minimum number of polygons in order for produce a 3D solid based on these textures?
• How many polygons -- how much of a mesh -- do we have to have in order to generate a "reasonable" 3D model?
• What is the maximum*?

Dr. J is 5'9" (1.75m), his elbow-elbow width is approximately 24" (0.61m) and his front-back is 11" (.28m) at the belly.

(*this is a trick question)

Dr. J Model 0 - Stuck in a PhoneBooth, Hardwired Code

    drawavatar( ? (world.Rooms) )

procedure drawavatar(r)
    # place randomly in room r
    myx := r.minx + ?(r.maxx - r.minx)
    myy := r.miny
    myz := r.minz + ?(r.maxz + r.minz)

    # ensure a meter of room to work with
    myx <:= r.minx + 1.0; myx >:= r.maxx - 1.0
    myz <:= r.minz + 1.0; myz >:= r.maxz - 1.0

    PushMatrix()
    Translate(myx, myy, myz)
    WAttrib("texmode=on","texcoord=0,0,0,1,1,1,1,0")
    Texture("jeffery-front.gif")
    FillPolygon(0,0,0, 0,1.75,0, .61,1.75,0, .61,0,0)
    Texture("jeffery-rear.gif")
    FillPolygon(0,0,.28, 0,1.75,.28, .61,1.75,.28, .61,0,.28)
    Texture("jeffery-left.gif")
    FillPolygon(0,0,0, 0,1.75,0, 0,1.75,.28, 0,0,.28)
    Texture("jeffery-right.gif")
    FillPolygon(.61,0,.28, .61,1.75,.28, .61,1.75,0, .61,0,0)
    PopMatrix()
end

Dr. J Model 0.1 - Stuck in a PhoneBooth, S3D File

// version
103
// numTextures,numTris,numVerts,numParts,1,numLights,numCameras
4,8,8,1,1,0,0
// partList: firstVert,numVerts,firstTri,numTris,"name"
0,8,0,8,"drj"
// texture list: name
jeffery-front.gif
jeffery-rear.gif
jeffery-right.gif
jeffery-left.gif
// triList: materialIndex,vertices(index, texX, texY)
0, 0,0,256, 1,0,0, 2,256,0
0, 0,0,256, 2,256,0, 3,256,256
1, 4,0,256, 5,0,0, 6,256,0
1, 4,0,256, 6,256,0, 7,256,256
2, 7,0,256, 6,0,0, 1,256,0
2, 7,0,256, 1,256,0, 0,256,256
3, 3,0,256, 2,0,0, 5,256,0
3, 3,0,256, 5,256,0, 4,256,256
// vertList: x,y,z
0,0,0
0,1.75,0
.61,1.75,0
.61,0,0
.61,0,.28
.61,1.75,.28
0,1.75,.28
0,0,.28
// lightList: "name", type, x,y,z, r,g,b, (type-specific info)
// cameraList: "name", x,y,z, p,b,h, fov(rad)

S3D Rendering, Version 0

Design note #1: parsing and rendering constitute enough behavior to go ahead and make a class (or maybe a built-in) out of this. However, Jafar has written far more sophisticated code we will prefer to use.

Design note #2: while we can make a generic S3D renderer fairly easily, to animate body parts (legs, arms, etc), our model will need to insert Rotation capabilities at key articulation points. We will consider this and the S3D part mechanism after we get "out of the box" into a higher polygon count.

Performance note: in "real life" there are polygon "mesh modes" that would allow several/many triangles in a single call. This is the kind of thing that using Jafar's classes would give you, over doing it yourself. Note that at one time I began planning a u3d file format as a minor simplification based on s3d.

procedure draws3d(r)
   loads3d("drj.s3d")
   # place somewhere in room r
   myx := r.minx + ?(r.maxx - r.minx)
   myy := r.miny
   yz := r.minz + ?(r.maxz + r.minz)

   # ensure a meter of room to work with
   myx <:= r.minx + 1.0
   myx >:= r.maxx - 1.0
   myz <:= r.minz + 1.0
   myz >:= r.maxz - 1.0

   PushMatrix()
   Translate(myx, myy, myz)
   WAttrib("texmode=on")

   every i := 1 to triCount do {
      tri := triangleRecs[i]
      v1 := vertexRecs[tri.vi1 + 1]
      v2 := vertexRecs[tri.vi2 + 1]
      v3 := vertexRecs[tri.vi3 + 1]
      Texture(textureRecs[tri.textureIndex + 1]) |
	 stop("can't set texture ",
	      textureRecs[tri.textureIndex + 1])
      WAttrib("texcoord=" || utexcoord(tri.u1,tri.v1) ||
	      "," || utexcoord(tri.u2,tri.v2) ||
	      "," || utexcoord(tri.u3,tri.v3))
      FillPolygon(v1.x,v1.y,v1.z, v2.x,v2.y,v2.z, v3.x, v3.y, v3.z)
      }
   PopMatrix()
end

Getting Rid of the Telephone Booth

Chad and Eric Say ...

1. You should start by learning to draw, and draw detailed sketches of front, side(s), and rear of your character.

Since we aren't artists, I will settle for digital photos. But you could substitute a drawing of yourself if you preferred.

2. You should draw a polygon outline (profile) from the side view. The number of polygons might initially be low (20-30?). Each is an (x,y).

3. You extrude yourself by taking each (x,y) and making a right and left side (x,y,z) from it. z's can be taken my measuring your front view width, or measuring yourself in RL.

4. You map textures

5. You refine iteratively by editing vertices and adding surfaces.

.X File Format

• Invented by Microsoft
• Both binary/compressed and human-readable XML-based formats.
• In Unicon, uni/3d/ provides class libraries (4.8K LOC, by Jafar)
• uni/3d/viewer provides a .x (subset) viewer
• uni/3d/models includes a sample model.

• Microsoft .x format specification is at http://msdn.microsoft.com/en-us/library/bb206258%28v=VS.85%29.aspx
• http://www.xbdev.net/3dformats/x/xfileformat.php
• http://paulbourke.net/dataformats/directx/
• http://www.cppblog.com/flashboy/archive/2009/05/20/83507.html

Thoughts on a 3D Pirate Ship

• This particular example gives us some food for thought looking forward.
• Obtained as a free download from TurboSquid; view license
• might not allow us to sell anything using it
• 864 polygons, Microsoft .x format
• Almost can load as-is with Unicon .x loader, not quite (quads)
• Want to be comfortable using industry-standard format / data structure in our own games and virtual environments
• want to connect our code to it in meaningful ways.

• Pirate ship.x -- 12K lines of modelly goodness.
• Generating these things is beyond the scope of this class.
• Using these things is not.
• Pirate Ship textures:
• ~15 different textures rolled into a single (1024x1024) .png file.
  

Next let's see what the Rabin chapter on Character Animation has to say about 3D Modeling. Chapter 5.2, Character Animation (Chapter 5.2, original).

(lecture covered slides 1-14). Lecture 19.

Discussion of Midterm Examination

Where we are at

• Schedule says we should have an A/I unit this week; we introduced some topics from it earlier
• Lecture notes say we should talk about networking and multi-user games
• Gut feeling says we have a lot more to say about 3D modeling and character animation.
• Extended discussion of midterm last session == HW5 extension
  One week: if you need more than that you are doing too much. Representation: prototype w/ single (texture-wrapped) primitive for avatars, then refine
• Plan: this week we will talk about A/I and use any time that remains to work on Avatars and/or character animation.
• Rationale: A/I is vital in almost all games and may contribute to HW5.
• We will have one more "Virtual Environment Experiences" assignment (last one was SecondLife), and one more programming assignment (Semester Project) after the current FPS assignment (due in one week?)
• In Moscow: Dr. Soule's seminar after class today sounds real interesting

Minecraft Demo/Discussion

Another .X model Example

from: warrior.x and warrior.gif

Rabin of the Day

Lecture 21.

Rabin on AI/Pathfinding (backup backup)

Discussion of u3dviewer

Reflections on "A/I week"

• How much sensing, thinking, and acting can be done in HW5?
• Sensing:
  • level 0=mob is a rock, no response
  • level 1=tactile (senses attacks, sometimes their sources)
  • level 2=hearing/smell (senses near-proximity)
  • level 3=seeing (senses farther off)
  • physical model? or just saving throws + modifications?
    • character could have base obtrusiveness value based on size/class
    • modifications for distance, other sights/sounds, monster alertness
• Thinking:
  • assess attitude towards (cause of) sensed event, e.g. player
    • models include: hardwired (kill-on-sight), alignment, to race/faction
    • how much would this monster really know about player X?
  • assess relative strength of self vs. opponent (fight or flight?)
    • what stats are directly observable?
    • what stats might a monster infer, or guess, and from what?
  • select a response plan
    • basic plans
    • how often should plans be revised or replaced?
• Acting:
  • movement (towards, away)
  • attack or defend
  • communicate (w/ neighbors or opponents)

Rabin: Character Animation (cont'd)

What are the important parts of Chapter 5.2, Character Animation (Chapter 5.2, original).

Lecture 22

This week:

• multi-user gaming, particularly networking, including Rabin chapter 5.6
• cover chapter 5.5 (Audio) later
• the CVE virtual environment and its implementation
• maybe Rabin 4.2 (collision detection) on Thursday.

Multi-user Games

• TCP, IP, and UDP
• (internet) ports
• packets and streams
• latency and bandwidth
• clients and servers
• synchronous and asynchronous

While this course isn't about networks, games use them and it is appropriate to provide a brief introduction to network programming. Especially if you have never done network programming before, you should read Chapters 5 and 15 of the Unicon book for a discussion of network programming in Unicon. For other languages you wish to use, you should seek out (and try out) their comparable functionality.

The main networking buzzword: Protocol

Two major families of protocols

• They are: stream-oriented and packet-oriented.
• Packet-oriented protocols might specify fixed, constant-sized packets. Examples are usually low-level (ATM switch, ethernet, WSN...)
• Many protocols including the internet protocols IP, TCP, and UDP are packet-oriented and specify the exact binary layout of data within fixed-size headers, followed by variable-length data payloads which can be either binary or textual.
• For example, IP specifies 20 byte headers.
• Packet-oriented protocols tend to be "efficient" but "non-portable"; the network delivers C struct data intact.
• Packet-oriented protocols are more effective when working on a homogeneous set of machines (all the same CPU, etc.).
• Software that has to run across machines with different byte ordering or CPU wordlengths benefit less from, and have to be careful of bugs when dealing with such binary data.
• Differences in compiler and operating system may also result in differences for protocols that have to run portably, especially for packet-oriented protocols.

Stream-oriented protocols are usually more human-readable, with ASCII text line-oriented message formats. For example, HTTP protocol sends its headers as a sequence of lines with a easily readable format like:

Fieldname: value
Fieldname2: value2

Rabin

Chapter 5.6 (5.6, backup).

Lecture 23

Network programming examples from the Unicon Book

Review chapter 5. Be able to describe open() modes "n", "na", "nl", "nu", "nua". read about the select() function.

Connecting in Unicon

   f := open("machine:port", "n")

Once the connection is open, the program has a file opened for reading and writing. Care must be taken to design communications so that no deadlock can occur where both sides are waiting for the other. In many client- server applications there is a strict request-response format to the communications.

Receiving a Connection in Unicon

In any case, a server requests an incoming connection from a client with

   f := open(":port", "na")

   f := open(":port", "nl")

Accept mode "na" will block until a connection is received. Listener mode "nl" will open an incoming connection partially ("listening") without waiting for a connection; it must be used with the select() function. When a listener is passed in to select() as one possible communication that might happen, and when an incoming connection actually occurs, the "listener" is converted into a regular opened connection. This is handy in servers, and enables them to serve multiple callers without having to use "threads".

select()

while *(L := select(f1,f2,f3,timeout)) =  0 do handle_timeout()
every f := !L do {
   ... handle a read on one of f1, f2, or f3 where input is available
   }

Look at the Examples in Chapter 15 of the Unicon Book

Addition to the book! From our experiences writing a multiuser virtual environment, we ended up adding a new function to Unicon named ready(). ready() is like reads() except that it is non-blocking. It returns immediately with available data, rather than waiting until data arrives ready() has proven essential in CVE.

Scalability and Multi-user Gaming

bandwidth

this is the "easiest" limit to remember, most of us know our internet connection can only transmit so many bytes per second, so transferring big files will take time. What you need to add to that knowledge is that during the same connection, bandwidth fluctuates wildly as other internet traffic varies. Also, across a WAN the bandwidth is limited by the "weakest link", so on my office machine with its gigabit network, connectivity to NMSU is only 1.2 megabits/second, and this factor of 800 slowdown varies from second to second (from 800X slower than the computer's NIC can handle to 1600X to infinity). Compressing files might take many billions of CPU instructions but still greatly speed up a large transfer; it is a typical bandwidth-reduction mechanism.

latency

the delay between sending and receiving packets also varies from very low to very high. Typical across campus latencies might be 50ms (up to 20 times per second? up to 10 round trips per second?), while latency across the internet is often in the 1.5 second range. Multiuser games have to be designed to not depend on low latency; for example, a "heartbeat" to keep all players in sync is a tempting idea, but if local client redraws waited for such a heartbeat, you would not get a high enough refresh rate for a smooth animation. Dead-reckoning is a typical latency-compensation mechanism.

# of packets

The bandwidth may be near infinity, the latency may be no problem, and the network may still impose limits: each packet costs the OS a lot of processing time to handle, whether it carries 6 bytes or 1.5KB or more. Packet aggregation is a typical packet reduction mechanism.

GPU

A GPU may easily be a limiting factor on the # of users. If graphic updates/changes are proportional to # of users, or # of polygons to be displayed is proportional to # of users, adding more users will gradually break the client's ability to update, starting with low-end non-GPU computers and working up even to high end machines. Level-of-detail is a typical means of compensating for limited GPU resources.

CPU

A CPU may easily impose a limit on # of users, CPU's handle core gameplay and user interaction plenty fast, but games tend to dump lots of extra work on the CPU, assuming it is an infinite resource. If you are on a low-end CPU, you may save CPU cycles by NOT doing a lot of the other limitation-reducing techniques which suck CPU resources. Switching to more efficient algorithms and data structures, and doing profiling and performance tuning are other typical CPU-saving techniques.

Main memory

Main memory is usually a major bottleneck in modern computing systems.

OS

Any time you interact with the operating system will greatly slow your program down. Whole careers have been built on the art of reducing the number of OS calls. For example in MS-DOS days the standard thing to do was to skip the OS and write directly to video memory for fast graphics. In modern UNIX and Linux systems, processes were too slow so threads were invented, and OS threads were too slow so "user threads" were invented.

disk

A program that spends time waiting for disk I/O may not be able to sustain game-level refresh rates. Many disk operations can be avoided by leaving files' contents in main memory, and only writing changed items out to disk periodically.

How to Handle More Users - discussion of processes and threads

This was immediately followed by a "fork-exec" model, in which each incoming connection triggers a new process, so that multiple users can be served simultaneously. Separate server processes for each user gives good fault tolerance (one user's server process crashing might not affect others') and poor/slow communication for applications where users interact with each other via the server.

Since process creation is slow, "fork-exec" has been replaced by various newer models, including farming the work out to a pool of pre-created processes, and using threads instead of processes.

Context switching between processes is very slow, and even switching between threads is pretty slow. In addition, communication between processes or even threads is slow. For these reasons, modern multi-user servers might have each thread handling several user connections -- especially if certain users tend to communicate together a lot. The number of users per thread might depend on how CPU-intensive the server threads' tasks are in support of each user -- if the server has to do a lot of work for each user transaction, it is easier to justify a separate thread for each user.

Are Virtual Environments only for Large Corporations?

I am not the only person crazy enough to propose garage-scale MMO development. Note that without a certain level of 3D graphics capability we cannot undertake this goal at all, and unless we find a way to make 3D graphics quite easy, it is far beyond our available resources.

Introduction to OpenWonderland and OpenSim

• Sun's OpenWonderland is a Java-based "Toolkit for Building 3D Virtual Words".
• OpenSimulator is a "more open" clone of SecondLife that strips out a lot of unnecessary stuff.

Introduction to CVE

• CVE implementation "book"
• http://www2.cs.uidaho.edu/~hani/cve_binary/setup-cve-test.exe
• The best way to get current source code at present is via SVN per instructions at http://cve.sf.net (source .zip files exist but need updating)

Chapter 4.2, Collision Detection

Chapter 5.6 (5.6, backup).

Lecture 24.

Homeworks

• HW#5 is due today. If you need more time, my late policy will be just as lenient as my grading is tardy. Still, you should finish it up ASAP so you can work on...
• HW#6
• HW-CVE

• Chapter 5.5, Audio Programming (backup)

More on Virtual Environments

Hard Technical Subjects in CVEs

Because writing a CVE is potentially so incredibly technically challenging, there is a danger that the only people who can do it are large multi-million-dollar industry labs. In this class we are interested in CVEs as vehicles for both direct and indirect research:

• research results that enhance the value/usefulness of CVEs (CVEs as a direct research domain; communication/interaction/etc.)
• research results that reduce the difficulty of writing CVEs (CVEs motivate research in programming languages and systems)

CVEs as Places for Action and Interaction

• textual chat; talking and listening
• by seeing each other, waving, smiling, etc.
• by following each other to specific locations or shared experiences
• by manipulating objects in the virtual environment. The objects might correspond to real-world artifacts: files, printers, etc.
• by creating new objects or spaces in the virtual environment.
• by recording an experience for others to view at a later time
• ??? how about some suggestions ???

Collaborative Work

• A CVE exists for a Purpose; people use it to Do Something.
• CVE's are inferior to real-world collaboration facilities. Under what circumstances do they make sense?
• A CVE provides a shared context among users. They should be able to see the same things.
• A CVE supports awareness of others: users should see each other.
• A CVE enables communication between users.
• A CVE might allow multiple, flexible viewpoints.

Shared Context

Awareness of others

There is foreground awareness and background awareness. Things should be in the background unless/until they start interfering with what you are doing.

Background awareness may include users' real locations and schedules, whether they are at their keyboard and looking at the screen at the moment, what task they are performing, etc.

Communication

CVE's and Entertainment

With a compelling proof-of-feasibility like Everquest in mind, we cannot help but believe that a CVE will soon dominate many fields of remote communication and endeavor. It is only a matter of time before CVE's are used for distance education, virtual dating and sex, live theater, circus and other public performances, as well as major meetings such as conferences, associations, and the activities of governmental organizations.

lecture#25

Attention Students!

Mike Griffin, the former Administrator of NASA (appointed by President Bush), will be on campus on Monday, April 18. He will be meeting exclusively with students at 10AM in the Commons Whitewater room.

If you are interested in attending the Student visit at 10AM, please let me or Becky Highfill know (bhighfil@uidaho.edu). There are a limited number of seats available and its very important that we know how many students are planning to attend. If you have any interest in NASA, space exploration, aerospace engineering, or space systems and technologies, this will be a very interesting meeting.

Thank you,

Brittany Harding
Communications Assistant
nasacomm@uidaho.edu

Audio in more HWs

• audio effects for combat
• alerts marking change of state in the game (ship sighted, land ho, arrival in port etc)
• introduction and winning/losing
• theme music for major zones (soundscape?)

Rabin

• Chapter 6.9, Audio Design (backup)

Content Creation

visual/graphical content

composed from 3D primitives, includes both static and dynamic/behavioral content. Our conspicuous examples are SecondLife and Minecraft.

things to do in-game.

part of this is game design/mechanics/coding. When is it content creation? We mentioned a few examples of this previously, such as City of Heroes' architect facilities.

One of the reasons to study content creation is to test its limitations and see what ideas ought to be present in future virtual worlds we might build.

Creating 3D Primitives

In SL, you can only build where either (a) you own the land, or (b) certain designated "sandboxes" or permission is granted for you to build. You can't own land without a premium ($10/mo, or 6/mo on yearly subscription), so you may want to start in a sandbox. I subscribed in order to buy my plot. It turns out for your first purchase of land you can buy 512 square meters (sort of a homestead) at a steep discount. Since I wanted to build a virtual Janssen Engineering Building, this was not big enough.

Off-hand, Second Life's construction tools look like a very reasonable and general mechanism for making virtual things, certainly much nicer than writing code by hand, or even having to produce 3D model files, for everything. It would be interesting to study their network protocol for such objects. The axes (z is up, instead of y) is probably intuitive to everyone except programmers.

LSL

The LSL is documented at http://lslwiki.net/lslwiki/wakka.php?wakka=HomePage

LSL is vaguely Java-ish, but not really very similar despite their claims. Every script is a "finite state machine", more in the software engineering design sense than the theory of computation sense. The set of events that can happen is predefined/hardwired in LSL; very different from Java where you define what methods your object responds to.

default {
touch_start(integer total_number) {
   llSay(0,"Hello World");
   }
}

default
{
    state_entry()
    {
        //llSay(0, "I am the avatar of hoops!");
    }

    touch_start(integer total_number)
    {
        llSay(0, "Woo hoo.");
        llSetColor(<1,0.7,0.7>, ALL_SIDES);
        state bouncing;
    }
}
state bouncing {
       touch_start(integer total_number)
       {
           llSay(0, "Ho boy.");
           llSetColor(<0.5,0.25,0.25>, ALL_SIDES);
            llApplyImpulse(llGetMass()*<0,0,15>,FALSE);
           state default;
        }
}

Minor aside: Linux computers behind CSAC can run the JEB demo. Add /net/faculty/jeffery/unicon/.bin.linux to your path to get Linux x86 Unicon binaries, and then compile away.

SecondLife comments

Some obvious statements:

• the 1520m has a maximum number of primitives allowed, something like 345, maybe a little higher. This is not enough primitives for a "detailed" representation, even though I paid "a lot" of money for the land. Second Life is a land of crude approximation. C'est la vie. Why is this limit important for SecondLife? What does it mean for builders?
• In CVE our entire concern so far has been internal to our building, but in SecondLife the building must obviously include an exterior. In fact, the exterior may be kind of important, and will "eat up" a measurable fraction of our allowed primitive count. Also, we have to include primitives for internal connections that aren't yet present in anyone's .dat but are needed to provide full connectivity. I am not sure Second Life's teleport capability is precise enough for us to reach our unconnected rooms (what a cool idea for dungeons/torture chambers). Upshot: you may have less than 20 primitives.
• Given this hard limit on primitives, we can't afford to duplicate any walls between adjacent rooms. The jeb* demos and CVE software is VERY naive in this regard, not minimizing its primitives at all.

Creating Activities

City of Heroes' Quest Creation Tools

JEB3

Avatars in CVE

Proposal: add 3D model file "parts" for each avatar body part in the model. Write a new subclass of Avatar and of Body Part to work off of (and be populated from) the S3D data.

Notes on the .dat parser/model constructor

procedure parseroom(s,f)
local t, r
   t := parseplace(s,f)

   r := Room(t["name"], t["x"], t["y"], t["z"],
	      t["w"], t["h"], t["l"], t["texture"])

Procedure parseplace() builds the table (a set of fieldname keys and associated values). The place is terminated by a "}", when it is by itself and not part of a field (parsed here by parsefield()).

procedure parseplace(s,f)
local t, line
    t := table()
    while line := readlin(f) do line ? {
	tab(many(' \t'))
	if ="}" then break
	if &pos = *&subject+1 then next
	parsefield(t, tab(0), f)
    }
    return t
end

procedure parsefield(x,s,f)
local field, val
   s ? {
      tab(many(' \t'))
      (field := tab(upto(' \t'))) | {
	  write("fieldname expected: ", image(tab(0)))
	  runerr(500, "model error")
      }
      tab(many(' \t'))
      val := parseval(tab(0),f)
      if field=="texture" then val := world.find_texture(val)
      if (field == "action") then {
	 /(x["actors"]) := []
	 put(x["actors"], 1)
         }
      x [field] := val
    }
end

procedure parseval(s,f)
local val
   s ? {
        tab(many(' \t'))
	if val := numeric(tab(many(&digits++"."))) then return val
	else if ="Wall" then return parsewall(tab(0), f)
	else if ="[" then return parselist(tab(0), f)
        else return trim(tab(0))
    }
end

If we chase inside parselist() we would find that other virtual objects must appear inside a list object, while Walls do not. It seems odd (and bad design, basically) to single out Wall() here as a special syntactic entity.

Dr. J should add additional notes here on parsewall() and parselist().

The recommended way to test your room data + textures is to run your sample data on the jeb1 demo. At least one student reported the jeb1 demo not running for them on Windows. If ran for me on Vista laptop and on XP on VMware on Linux... but if you are having difficulties, see me for help, or try another machine. Oh: what image file formats are you trying to use? .gif is safe. .jpg and .png are "maybes". libjpeg worked on linux and not on windows last time I checked. Jafar claims we have libpng support, but not sure if that's gotten built into windows yet or not, either.

Virtual CS Project Update

Announcements

No class next Tuesday !

I will be in Idaho Falls visiting UI and giving a lecture there in CS578 (neural networks design). I am looking into whether I can do a lecture topic of mutual interest (biologically-inspired game A/I) and get it recorded for you-all, but as of now, no class.

Flip Flop !

Earlier I said we'd do in class demos on May 5, but I think 75 minutes will not be enough time. Since the final exam will be a take-home exam, I intend to use our final exam period (Wednesday May 11, 12:30-2:30) for in class demonstrations and discussion. I will post the take-home midterm exam on Thursday May 5 but it will not be due until Tuesday May 10.

CVE update

New Windows binaries are posted. For source code, the svn repository holds the latest.

Rabin

• Chapter 6.1, Visual Design
• Chapter 6.2, 3D Modeling
• Chapter 6.3, 3D Environments

The Server and Protocol

Developing n-User Chat Capabilities

• chat window is utterly stupid, doesn't use GUI classes
• server seems to recognize logouts pretty well; may need more work
• client does not currently handle disconnects/reconnects
• fairly easy to reorganize the main event loop to where it feels slow

Server State and Network Protocol

A CVE Network Protocol, draft

Lecture 27.

Announcements

Class next Tuesday: "Biologically-inspired Algorithms in Game A/I"

Joint with CS 578. If you have no other class at 12:30-1:45, you can attend in JEB 026 at that time. Otherwise, I think EO will make a video available, but since it is irregular, it will take some manual effort and a longer than normal time to get that video in place.

CVE Class Time Online

We will hold a class session in CVE a week from today (April 28). We will do it in the regular classroom, probably for half the session. Please check your timestamps and update to a new/current CVE client before then, possibly the night before or the day of the session. The goal will be to facilitate the completion of the hw-cve.html assignment, and since this is research software, we see how many crashes and how many reboots we will get.

HW#3

Have read through the code and nearly finished grading, except for mechanics/playability/strategy points. (graded: Stinger/Kimball/Mazur/Vollmer/Nance/Miller/Norris/Flynn). If you turned in a HW#3 and aren't on this list, please double-check with me to see if your HW got eaten by the UI mail-troll.

System Challenges for Multiuser Online Virtual Environments

• Glueing together the solutions for individual components of the problem is not guaranteed to work.
• Latencies are inevitable; consider how to deal with them from a user's perspective.
• Distributed Legible City - (multi-user) bicycle VR with audio link. What system challenges does this reveal about VR-oriented VEs?
• Engineer something to do, or something to care about. WoW or LOTRO fall flat for some users because their many things to do are irrelevant. Many VE's have far less to do than do the MMO games. Of course one can talk about the VE as a technical or artistic achievement, but what else?
• The behavioral quality lacking in VE's isn't due to lack of high-powered AI but due to the need for simple reasonable behaviors to be modeled for large numbers of everyday real-world objects.
• Environmental properties - how much ordinary behavior can be applied to all objects, because it is a property of the environment?
• Use multiple inheritance (environmental behaviors + object-specific behaviors)
• not just an Environment: a range of environments. Suggests either: (A/I) generation algorithms, or user-creation, may be more attractive than the hundreds-of-pro-artists dev model
• Explicitly separate the (virtual world/simulation) model, from each user's perception of it.

Understanding Network Requirements for CVEs

• Almost all network requirements derive from user behavior.
• Do users speak at the same time? That takes a more bandwidth than simplex audio
• Users are moving 15-45% of the time, and speaking 5-30% of the time. Can we use that to calculate bandwidth at the server? Greenhalgh's numbers are around 2KB/sec for motion (for 6fps), 2KB/sec for audio. This would be marginal on a 56Kbit modem (40Kbit connection = ~4KB/sec). Greenhalgh mentions that other systems economize for motion. Jeffery suspects VOIP often uses > 2KB/sec
• Peak bandwidth will be higher if users' activities are highly coordinated. For example, if users are all instructed to do something at the same time.
• Three key actions: user movement, user audio, and discovering new objects and users. Invent methods to make these cheap; invent methods to scale them to users' bandwidths.
• Design a system to be as general as possible; only optimize heavily-used parts.
• DIVE idea: use standard WWW servers to serve up our data? Alternate: use a SQL database to serve up our data?
• MASSIVE-1: on 10Mbit ethernet, maxed out at 14 users

Distributed Architecture Implications

• indoor vs. outdoor
• zone structure
• who can see what and whom
• how many users? (more requires being able to restrict what's transmitted)
• the dynamics of the world (can you blow up walls?)
• the extensibility of the virtual world - can new objects be introduced on a live server, or only by shutting down, recompiling and sending out new executables to all users?

CVE Extended Demo

CVE: Following Execution Across the Net

	 put(grouping, moveuid || "part " ||  name || " " || dir || " " || ang)

   method flushnet()
      if session.isUp() then {
         session.Write(grouping)
         grouping := list()
	 }
   end

# server.icn::run()
         if not (L := select( socket_list, Ladmins )) | *L=0 then next
...
                  if buffer2 := Tsock_pendingin[sock] || sysread( sock ) then {
...
                     buffer2 ? {
                        while buffer := tab(find("\n")) do {
                           ExecuteCommand( sock )
...
            "move":   {
           dynStHandler.saveAvatarState(Cmds,sock,Tsock_user, parsed[2])
           dynStHandler.getRecepientUsers(Cmds, sock, Tsock_user,
                          Tuser_sock, TrecpUser_sock,
                          "AvtMove",parsed[2])
           sendtoSelected(sock, TrecpUser_sock, parsed[2], "move", 1)

CVE Source Code: the Next Level of Detail

Biologically-inspired algorithms in game A/I, delivered from Idaho Falls.

• talk slides (ppt, pptx)

Lecture 29. Research Topics in Virtual Environments

Rabin

• Chapter 6.4, Texture Mapping

Reading Assignment

• Read the evogames papers from Tuesday's lecture on game A/I
• Check out cves.html. Read the paper on network traffic (Wolff, Roberts, Otto).
• find me at least ONE new link that is not on my cves.html site that is about virtual environments, that is, shared 3D persistent online multiuser applications (first come first serve).
• On your final exam, be prepared to discuss the ideas from these (the evogames, cves.html, and "Research Links" forum topic) papers. Google around for "virtual environment", "artificial environment", etc.

Network Protocols for CVE's (Greenhalgh)

• Unicast vs. multicast (IP multicast, Deering and Cheriton)
• Reliable vs. unreliable (unreliable OK for audio!? unreliable OK for moves) (what properties of a given communication make it OK to be unreliable?)
• selective reliability
• Disadvantages of client/server: server will do more processing than a multicast router would. server limits scalability of the system.
• Greenhalgh's experience: servers haven't been a major bottleneck.
• Advantages of client/server: single network connection, more effective congestion control, more reliable, ability to combine/piggyback messages to a given user, server can perform extra processing/filtering on messages, for example, summarize a sequence of messages in a single message.
• General heuristic: use multicast for unreliable location connections, client/server for everything else

Last Tuesday's lecture?

• talk slides (ppt, pptx)

Class Project Demos During Scheduled Final Exam Slot

Games and Virtual Environments Virtual Expo

Presence in Shared Virtual Environments (Buscher et al)

Methods of locating someone else in virtual space. Some of these are graphical, some textual, and some could be either. Perhaps some CVE's would eschew some of these techniques in order to be "realistic". What other methods can you think of?

• Landmarks ("meet at the bridge")
• Coordinate systems ("meet at 538,-111")
• Virtual "GPS" (computer provides pointer to any person you specify)
• "Yelling" (computer provides approximate direction of person when they ask)
• Teleporting them to you, or you to them
• Peeking (being able to look at their screen, i.e. through their "eyes")

The Problem with 3D Environments

• Reduce 3D down to 2D navigation (most of the time)
• Provide automatic navigation (most of the time)

Themes

Avatars

Bandwidth, scalability, and fundamental limits of hardware

Augmented virtual reality

Obvious Things About Commercial Game Virtual Environments

• MMRPG's are a spectacular technical and commercial success. Everquest introduced or popularized many technical concepts as well as a genre and business model which others like City of Heroes have imitated and improved upon. The per-boot update patching model is a good example.
• These games are very large, complex, expensive, and demand a high powered computer, especially a powerful graphics card. Everquest II will not run on my laptop with 64MB dedicated NVIDIA 3D chips; WoW does, and so does City of Heroes. Guess which games I am more likely to subscribe to?
• These games use surprisingly little network bandwidth, but latency is a huge problem, as is server scalability for large numbers of users
• MMRPG's are high-powered chat engines. There are multiple simultaneous sets of users you are chatting with: individuals, people in your immediate vicinity in 3D, people in your "zone", people in your per-session "group", people in your persistent "guild"
• The graphics and chat are competing with each other for space and user attention.
• The world is real-time. Chatting can get you in trouble if a monster comes up and starts attacking you while your keyboard is tied up in a long chat.
• The graphics has a lot of static stuff that just sits there and doesn't "do" anything...pro: makes the world more "immersive"; con: users can't burn it or chop it down, blow it up, etc. and this detracts from the realism. Newer games have less static stuff; Half-Life 2 brags about how you can destroy everything you see.
• Playing the game over a period, your character in the virtual world becomes substantially more powerful. The main Thing to Do is to try and acquire more power and/or more fame amongst your peers. This is a mixture of "experience" mainly acquired by killing monsters, and acquiring powerful magic items.
• The "zone" system really detracts from the realism

Unobvious Things About Game CVEs (MMOs)

• You pay $12-15/mo, it is not obvious that it should cost this much
• You pay periodically for new content (new zones, new creatures), the monthly fees are mostly pure profit.
• The graphics have gotten a Lot Better over time; machine requirements have gone up more gradually
• Success == More Players == Worse Gameplay == Drives people away. Scalability limits are partly social.
• The "Missions" in City of Heroes succeed in some senses, but are a major failure in many ways. They give players something to do, but because Everyone can do them, they violate the immersive realism, warp (verging on ruining) the economy, and cause exhaustive off-line cheat-reference-websites to be an important (nigh unto essential) part of serious gameplay.
• People play the game very differently to meet very different personal needs. There are people escaping real life, people seeking human contact, people trying to feel competitive/superior...
• Grouping with total strangers for random acts of violence is not realistic...but is by far the best and sometimes only way to advance. Play would benefit from an ebay-style alignment rating system.
• Because everything in the world is static except the players, the immersive reality is compromised by e.g. killing the same person or monster over and over again.
• Because players can't affect changes (build houses, take over cities) the world experience is controlled by Sony, not by players, and the rate of new content is slow, and the place becomes boring over time.

"Environment" Imposes Some Essential Features on CVE's

a CVE has a virtual world

This is a large space, typically with many locations and objects. Its goals are: make the user feel they are in that place, and make the user feel that within that place, they can accomplish their goals.

a CVE has time, and persistence

Things that happen in one CVE session affect later sessions. There is no "pause" button; the virtual world is happening whether you are there or not; things happen while you are out. Users do not ever "start over".

a CVE is reactive

CVE's content is user-controlled. Users do whatever they want, rather than following a script.

Additional "Desirable" Properties of CVE's

a CVE should be "realistic" as possible

laws of physics, day/night, weather, and graphical realism are all examples where the CVE doesn't have to work the way the real world does...but most CVE's will be more "immersive" and understandable to users if they reflect the real world.

a CVE should scale to handle "as many users as needed"

other people are a primary aspect of our real environment, and allowing only 4 people, or 16 people, isn't very realistic

a CVE should be richer than necessary

is it a "place", or just a chat/teleconferencing program?

Anatomy of a CVE

Users must be able to communicate

This implies Internet or other transport layer, plus common language or robust translation capability. "Language and translation" apply to both the network communication protocol and the human users.

Clients must be able to "render" the virtual world usefully

This implies sophisticated graphics software and a minimum hardware platform. In this class, I believe we can obtain or write sophisticated graphics software, but let us ask: do we all have access to minimum hardware?

Users' views of the virtual world must be (somewhat) consistent

There is a big problem if the time grows too long between your doing something and the time other users see what you do (latency). Some actions are more important than others in this regard.

New CVE Concept of the Day: Goal Assistance

In real-world-based CVE's, there may not be "missions" but there may still be goals, such as: complete a homework assignment so that it passes an automatic submission tester.

One interesting point is: people cannot always remember the details of their goals: where to go, what to do, etc. They sometimes wind up writing down the instructions they were given by a (computer-controlled) character in the game. It is sort of obvious that the computer should provide assistance with this task, provide some of the capabilities of a Personal Digital Assistant, such as a Todo list. City of Heroes does this rather nicely.

Scalability of CVE's

Robinson et al distinguish between upward scalability (more people) and sideways scalability (different people). Besides scaling users and groups, they argue for more different kinds of objects in CVE's, especially objects with real-world presence (machines, printers, files), where manipulating the object in the CVE causes real-world work to get done.

Should all this work happen inside the CVE? Robinson argues for the 3D part of a CVE to be only one of many different collaboration programs, complementing other forms such as document viewers, web, and audio/video connections. In support, they observe that the 3D CVE's usually overemphasize the people, while other applications usually underrepresent them.

They are arguing that all our mainstream applications should become CVEs and propose a VIVA architecture along these lines. There are many pros to this approach, such as accessibility and interoperability when 3D graphics are not available, from the web or a PDA, etc. What are the drawbacks to trying to make all our regular applications CVE's? Do Robinson et al identify those drawbacks?

Videoconferencing: a perpetual prince, but never a king?

Other ideas:

• A lot of energy is devoted to describing how they allow people to be aware of other people visiting the same webpage at the same time (big deal).
• No Fixed Starting Point; VR, web, word processor, etc. are all equal citizens of their CVE.
• VR's main or only value: background awareness of others. (Do you agree, or disagree?)
• Server-based architectures are limited by the server CPU, while peer-to-peer based CVE's are limited by the network capacity.
• Some CVE's support 3D if available; 2D otherwise.

Besides "master servers", VIVA uses at least 6 kinds of special-purpose servers. Traditional services of "VR servers": spatial data processing, collision detection, awareness and authorization services, environment partitioning. Dynamic repartitioning is seen as central to scaling to more users.

[Snowdon96]: A review of distributed architectures for networked virtual reality. Virtual Reality: Research, Development, and Applications 2(1), 155-175. gives a reference architecture consisting of:

• distributed system services (name server, trader, time service, resource discovery agents)
• security services
• object support services
• core VR services, e.g. collision detectors, world servers
• non-core VR services: application object
• user interface services
• other supporting services

Where we are at in the course so far

Notes while trying to test your HW#K

What, Binaries?

Of course I am very uninterested in binaries, I want source code and any resources (e.g. .gif files) bundled up (.zip is probably best, .tar or .tar.gz or other common formats OK).

Missing makefile?

Turn in everything I need to compile and run your program correctly, if you can. This would include a makefile or batch file in the .zip that you turn in.

Runtime error?

It is not uncommon in Unicon to get runtime errors, don't be panicked by them but do get practiced at reading them. A sample one is

Run-time error 107
File cve.icn; Line 244
record expected
offending value: &null
Traceback:
   main()
   make_SH167(...parameters...) from line 73 in please8.icn
   Room_add_door(...parameters...) from line 19 in please8.icn
   {&null . coords} from line 244 in cve.icn

Lecture 31. Future Trends in Games and Virtual Environments

CVE Status Report

• Hattrup added to CVE, Riley in progress, Jafar on deck.
• If what your room looks like in CVS is better than what you turned in, it will replace it for HW8 grading purposes.
• Multi-user / account creation somewhat more functional
• CVS and www.cs.uidaho.edu/~jeffery/setup-cve.exe updated
• Generalization from NMSU required reduction in "two-dimensional thinking"

CVE's Using Symbolic Acting (McGrath/Prinz)

• "chance meetings", "recruited conversations"
• sensing what people are doing and when they are available to chat (how do we build automatic "available to chat" sensors into our CVE?)
• ignoring people politely when we are busy

Symbolic Acting

In between silence and talking there is a continuum comprising mutual sense of presence, body movement, mutual gaze awareness, and the trajectory of body motion (towards someone, away from them, on a route unrelated to them, etc.). "Sleepy mode": avatar looks like an ice cream cone.

Contact Space and Meeting Space: the lounge versus the seminar room. The big difference is whether others can interrupt.

Nessie world: different rooms for different working contexts. Avatars are Lego puppets. Agent avatars signal time of day (waiters, janitors?), active virtual furniture shows external values and activities (temperature? stock values?). Projecting the CVE in the background: on the wall, or maybe on the root window?

Experience results: the "meeting space" won't be the focus during meetings, the focus is on the material presented, documents being reviewed, etc. People will want to customize their avatars, but do not need (or want) them to look exactly like in real life.

Who is talking in the CVE? Small window size means this vital information may need to be exaggerated.

When is symbolic acting unfortunate: when it embarrasses you publically, because you want to quietly working on something else (say, surf a website) while in a meeting in the CVE in another window. Sometimes you don't want the system reporting your every action to others!

More issues: security can be a problem; no one wants to have another account to login to; contact space needs to cooperate/integrate with e-mail, telephone, etc.; contact space needs to be accessible via PDA/cell phone, etc.

The Forum is not just chat, it is the ability to comfort, monitor, increase awareness, and observe others.

Dr J's idea of the day: "selecting" (clicking on) another avatar with your mouse might send an acknowledgement message to the other person, to let them know you are looking at them and they have your attention, as a precursor, if they wish to chat.

More on Modeling 3D Spaces

This course is not about 3D Graphics: we won't be covering advanced algorithms for photo-quality rendering like they use in the CG movies. But, everybody can learn enough 3D graphics to be useful for your project.

Some 3D Geometry

In practice, complex objects are composed from simpler objects. Each simpler object that is a part of the more complex object is given by specifying their location and orientation with respect to the complex object. This is how, for example, you might attach an arm to a torso, or attach different pieces to a table or lamp or whatever.

Location and orientation are more generally given by the operations Translation, Rotation, and Scaling. A basic result of early work in computer graphics was to combine and apply all three operations via a single matrix multiplication. We don't have to write the matrix multiplication routine, see CS 476 or a linear algebra class for that. We can just enjoy the fruit of their labors as manifested in our 3D graphics library (OpenGL) and a higher level API built on top of it.

At some point the "outermost" objects (say, an entire table or an entire person) are placed into the virtual world by similarly specifying the object's location and orientation with respect to World Coordinates.

Rendering an object in room coordinates example:

PushMatrix()
Translate(o.x, o.y, o.z) # position object within World Coordinates
o.render()		 # object rendered in Object Coordinates
PopMatrix()

Drawing Primitives

These primitives are further flexified by the Scale() function. When stretched (via scaling), primitives like DrawCube() can handle any rectangular shape.

Lighting and Materials

OpenGL has 8 lights, which can be turned on or off, positioned at specific locations, and can feature any mixture of three different kinds of light: diffuse, ambient, and specular. Diffuse seems to be the dominant light type, with the others modifying it. In the example:

   WAttrib(w,"light0=on, ambient blue-green","fg=specular white")

In addition, if you are not using a texture, the "fg" attribute for an object can include an object's appearance under the three kinds of light, and can include a fourth kind of light, emission, where the object glows all on its own.

   Fg(w, "diffuse light grey; ambient grey; _
          specular black; emission black; shininess 50")

One thing that was added recently to the 3D facilities is the ability to blend the texture and the fg color when drawing an object ("texmode=blend"). One thing that is going to be added in the future (as soon as I get a student to help) is to add a set of predefined / built-in textures ( "brick", "carpet", "cloth", "clouds", "concrete", "dirt", "glass", "grass", "grill", "hair", "iron", "marble", "metal", "leaf", "leather", "plastic", "sand", "skin", "sky" "snow", "stone", "tile", "water", and "wood").

Bad News? Midterm Exam?

Introduction to Networking in Unicon

Reading: Unicon book, chapters 5 and 15.

Networking support in Unicon was designed by Dr. Shamim Mohamed (Logitech, Inc. of Silicon Valley) with a little help from Clint Jeffery, implemented for UNIX by Shamim Mohamed, and ported to Windows by Li Lin (M.S. student) and Clinton Jeffery. These capabilities are simple, easy to use communication mechanisms using the primary Internet application protocols, TCP and UDP. Unicon also has "Messaging facilities", providing support for several popular network protocols at a higher level than the network facilities (HTML, POP, ...), done by Steve Lumos (M.S. student).

Networking for Non-nerds

Besides the IP number identifying a particular machine, most Internet services specify a port at which communication takes place; the ports serve to distinguish different programs or services that are all running or available on a given server. The ports with small numbers (say, the first few hundred) have standard services associated with them, while higher numbered ports can have arbitrary server-defined associations to custom applications. Ports providing standard services can usually only be run by the administrator of a machine; ordinary end users can generally use higher numbered ports.

Client-server and Peer to Peer

Configuring CVE's for Object-Focused Interaction (text Chapter 7)

• Engage with and share visible objects in the 3D environ
• many activities require talking and monitoring each others' conduct while looking at and using some workplace artefact.
• Earlier we said, selecting someone else should tell them they can chat with us. And we've said, we should see each others' cursors moving around within a shared text editor. More broadly this chapter is saying, we should be able to see what object others are selecting when it is not us; other users should not just have an avatar, they should have visible lazergaze, or a VR cursor. In RL we detect all this by watching each others eyeballs, but it will be hard to manage that in a CVE, we have severe resolution loss.
• Embedded video views that are dynamic texture maps attached to virtual objects
• Avatars should be able to point their arms in any direction they please; head should tilt to face that direction, to reinforce pointer. Lazer gaze, or glowing or highlighting the object-gazed upon, would be a more extreme method.
• Narrow field of view (55-60 degrees, 1/3rd of humans' normal viewing angle) can often cut out visible features of the other avatars (tunnel vision) (compare with driving a car; we need turn signals and frequent manual checks where we turn and look behind our car).
• Slow speed of movement makes it worse; harder to make quick glances.
• "peripheral lenses" extend avatar's field of view
• Beyond lazer gaze, other users fields of views can be made visible by making avatars into giant flashlights.

Look at Homework #4

Startup Time

Tiling textures

Making Textures Tile Properly

• http://www.highpoly3d.com/writer/tutorials/tileable/seamless.htm
• http://astronomy.swin.edu.au/~pbourke/texture/tiling/

Viewing Volume

Project Ideas

How Not to be Objective (text Chapter 8)

• Peripheral Awareness
• Informal Meetings - how to rig things to make this happen more often?
• Learning by Watching - how to make it easier to watch others do tasks?

Subjective virtual environments

Flexible Roles in a Shared Space (text Chapter 9)

"Kansas" - 2D, programming environment for the language "Self". Self is a delegation-based descendant of smalltalk.

"Field of view in most CVE's is so narrow that other avatars are usually off-screen".

• Roles may be implicit or explicit
• Roles may be temporary, have term duration, or be persistent
• Roles may be supported by explicit tools or locations
• Roles tend to evolve/change over time
• Roles may be associated with awareness information categories

Capabilities could be used anywhere in a CVE, but perhaps the user interface is a sufficient place for them. A capability can itself have a visible manifestation (like the piece of chalk, or the microphone). A "capability tray" might hold (and allow easy sharing) of a user's entire capability set.

Avatars

Social Interactions in Multiscale CVEs

social presence

how you look shapes/influences how others will treat you (social conventions)

Yo's avatar

Yo Sep has got an avatar that with a single stroke (head images) achieves more reality than the CVE in this 2002 paper.

ants and giants

it is easy for us to exaggerate differences in size, if we have a reason to do so. If you want to see microdetails, become an ant. If you want to walk from here to Albuquerque and see the Organ and Jornada ranges in a single hike, become a giant.

multiscale collaboration

for large complex structures, different collaborators may need to work/view the world at different scales (seeing different levels of detail). Example: software architects vs. designers vs. coders

dynamic sizes

a user might shrink or grow themselves to fit a situation

size in social domination

bigger individuals tend to dominate social situations

size in natural life

We all start out life as "newbies", and gain in size and ability. Ability in a CVE might include: movement speed, viewing distance and detail, having keys to certain rooms...

"size" in unnatural CVE life

More avatar upgrades might include ability to teleport, walk through walls, fly, etc. Besides size, avatars with more abilities might stand out via color, glow, louder (Jurassic Park-style) strides...

communication-centered vs. artifact-centered collaboration

CVE balances and supports both, but it is artifact-centered collaboration where it will shine or fail.

but avatars need (in general) to be visible

bad things happen in CVE's with invisible users

external min and max?

others' view of you may need to be capped, even if your own view of the world scales wildly

scaling is more than just calling Scale()

in general, smaller = render fewer details please. wire frames?

proxemics

study of proximity. Asymmetrical proximity when avatar scales are varying. Giant will "feel" that ant is far away, ant will "feel" that giant is real close.

proximity ranges:

• intimate = < 0.45m
• personal = 0.45-1.2m
• social = 1.2-3.6m
• public = > 3.6m

Two (or more?) avatars?

One for action, one for conversation? Daemon avatar, a placeholder for conversation (intercom) while one is elsewhwere.

Changing viewpoints

See from your daemon's eyes; see from others' eyes to know what they are looking at/talking about/referring to.

Scale-based semantic representations

Besides "adding detail" as a user shrinks and gets closer to what they want to look at, the representation may change (solid→molecule→atom→particle). The hard part would be to see relationships between objects at different scales/ representations.

imposters

at a distance, a much cruder representation of an avatar works fine

Designing Interactive Collaborative Environments

WWW3D and Web Planetarium

Big problem with scalability (too many pages to view). Cluster pages together into 1 sphere per site.

WWW3D shows very little page contents, mainly shows links; color codes pages by how recently they were viewed. Web planetarium uses the first image in the page as a texture (often a logo or person).

From public demo: users avoided following links to "warp" new sites into the 3D layout. They preferred to wander around a landscape that is already created.

The Blob

• mouse gestures (stroking, pulling, etc)
• "Local Tools" approach, not "menu and palette" approach. Each item may have several state attributes, and remembers them when set down.
• Forcing collaboration example: both users have to click an item in order to get/select it. But, its better to "encourage" than to "enforce" collaboration.

Robot-Human collaboration

• "deictic references", e.g. "this object here".
• Robot semi-autonomous; this is a collaboration tool not a remote control tool.
• division of labor between robot and human is fluid
• sometimes, too many details in the model is bad, focus detail around the job at hand.
• Pfinder, MIT Media Lab, extracts 2D+ information about people from a video feed (tracks hands, head, center)
• Path objects, which can be illuminated or autofollowed.
• PDA 2D map as aid to 3D navigation?

Trouble in CVE-Land

• configure script bogus? It had control-M's on it that caused some shells to choke (e.g. fedora core 3) but not others (updated)
• server connects but doesn't answer - a new kind of hang (fixed by killing and restarting server; needs investigation)
• server won't start at all? check if someone else owns the port
  their zombie iconx = you must use a different port
• can't run /sbin/lspci? Unicon version issue?

Tele-Immersive Collaboration in the CAVE Research Network

• EVL at UIC
• Their focus: "high quality collaboration" with few (< 8) users on powerful computers when bandwidth is plentiful.
• CAVE: an immersive 10x10x10 VR room using projection on walls.
• 3D shutter glasses, not heavy goggles; shutter glasses also report user's head position to VR system.
• 3 button "wand" in place of mouse; wand reports user's hand position to VR system
• High end silicon graphics workstations to drive displays
• Applications in C/C++ and OpenGL/Performer
• Several people can go in the same CAVE, but only one controls Eye position and carries the Wand.
• Tele-immersion = CVE's using VR hardware
• Capture and transfer gestures, audio, and video among collaborators? At least: CG versions of collaborators which show head and hand position. adequate for tasks, no good for negotiation.
• CALVIN - used CAVE to do multiuser architectural design. "mortal" and "deity" modes. "deity" mode sees the big picture, simcity-style, and good for gross manipulations; "mortal" mode better at fine manipulations.
• NICE - a virtual environment for young children; main activity is gardening.
• Non-humanoid avatars (e.g. bunnies); mouse-mode; ability of one avatar to pick up and carry another avatar.
• Persistent server; changes happen even when humans are not logged in.
• Giving a newbie a flower to welcome them to the environment
• Using the "hokey pokey" to test network quality
• Avatar nametags to tell which user is from where
• Virtual webcam for world monitoring
• Applications: car designers, meteorology, oceanography, medical education, history, virtual tourism,
• NICE suffered from lack of a clear goal; Round Earth (a successor to NICE) had a specific goal of teaching kids that the earth is round (woohoo); one kid sees the surface of a planet as an astronaut; the other sees the whole ball and plays the role of "mission control".

Lessons:

• having only one hand is a liability
• other remote users' avatars can block your view! \ignore command may want to do more than block chat.
• Long "beam" pointers are handy when pointing at distant objects
• Users will want to know what they look like to others.
• "Audio is the most important communication channel to maintain the shared collaborative space".
• Avatars need (at least crude) mouth movements corresponding to audio, so folks can see who is talking.
• People feel very bad when they accidentally walk through someone else; collision detection between avatars is important. However, when situations get crowded, the same collision detection can be a pain, so perhaps it needs to be dynamic. A body in motion is less of an obstacle than one at rest?
• Americans tend to gesture more than some cultures; gesturs inferred from real world (i.e. hardware VR) need exaggerating to be clear in the CVE.
• Newbies generally require a tourguide.
• Bad jitter is worse than bad latency

Future Work for the CAVE Folks

• Asynchronous work support in the CVE requires more study.
• "Vmail" - recording of an avatar talking and referring to objects in the virtual space. Recording most naturally belongs to the networking layer.
• Virtual sticky notes.

What I learned from this year's Halloween

Managing Dynamic Shared State (SZ Chapter 5)

consistency vs. throughput

it is impossible to allow dynamic shared state to change frequently and guarantee that all hosts simultaneously access identical versions of that state"

shared repositories

Variation: distributed shared repository, in which different dynamic state is managed on different machines. "Virtual" centralized repository.

Idea: how consistent your information about others is can be proportional to their importance to you or their proximity to you; this doesn't have to be a boolean visible/too-far-away condition. What about updating with frequency proportional to distance? Server could compute: should I send user X's move to user Y? with probability = (1.0 - distance) * (1.0 - direction)

frequent broadcast

Specific machine "owns" the object for which it broadcasts updates; more complicated for others to modify the state of that object. Works best in a LAN setting (many early LAN games used this model).

Concept: "lock lease" = locks that automatically timeout.

Latencies of 250ms are not uncommon on WANs.

Jitter = variation in latency from one packet to the next.

state prediction (dead reckoning)

prediction = how we calculate current state based on previous packets. commonly using derivative polynomials (velocity, acceleration, and possibly "jerk"). order 0 = state regeneration technique. order 1 adds velocity. order 2 (with acceleration) is "the most popular in use today". Note: if acceleration is changing each packet, using it generates a lot of errors. Good to disable acceleration dynamically when it is not helping, maybe use it when it is nonzero and consistent for 3+ updates in a row.

derivative polynomials don't take into account our knowledge about the semantics of the object. Separate dead reckoning for each class of virtual object?

convergence = how we correct error. instead of "jumping" to correct, we might smoothly adjust. goal = "correct quickly without noticable visual distortion". "snap convergence" just lives with the distortion.

linear convergence: given the corrected coordinates, predict where the object will be in 1 second. Now, compute the prediction values for the object so that it moves from its current, erring position to where it is supposed to be a second from now. (what if this runs through a wall?)

To do better: use a curve-fitting algorithm, maybe a cubic spline.

Reflections on a MOO scenario

• out of curiosity, thinks Dr. J, how usable/useful would our CVE be if we supported non-3D operation?
• commands "look" and "look becki". Do we need them? ("look" describes the room you are in. "look user" describes someone).
• "blink": a good name for an "I am not afk" command.
• "idle driving into the lab": tells others why you are afk and maybe gives them an idea of for how long.
• "wave", "nod", "laugh" etc.
• "paging": sending a message from another room; is this term more evocative than "tell"?
• advantages of MOO-mode: requires little CPU, unobtrusive,...
• major feature: avatar sits there listening to all conversation in a room even when you are not there, all you have to do is scroll backwards to review it (extra client commands to help with this)
• "persistence underlies the development of a notion of place - and places can make people feel like they belong and want to go back"
• "MOO room" = "project" or "group" area for chat. User-creatable.
• multiple avatars, having an avatar in a room means one is recording what's happening for later review.
• alert = key < 1 minute; daydreaming = key < 5 minutes; idle = afk < 1 hour; staring into space = away > 1 hour
• summaries during your absence: help you know whether to scroll back and look at the logs, and if so, what (or who) you are looking for.
• MOO downsides: whispers promote secretiveness; potential for disastrous typing mistakes; rooms promote and make conspicuous the social cliques, and perhaps make them subject to scrutiny.
• "more effort has gone into the creation and support of persistence mechanisms than any other type of development".

Reading Assignments

• [Zyda 2005] IEEE Computer September 2005, "From Visual Simulation to Virtual Reality to Games", Michael Zyda Google for the title.
• the TOP paper

All About Display Lists

In the case of 3D windows, we might use a similar strategy but instead keep a display list, which is a data structure that contains all the data about all graphics operations that have been performed since the last time the 3D window was opened or erased.

OpenGL has a display list concept, but its display lists would not be easily manipulated from the Unicon application level, so we maintain our own display list as a regular Icon/Unicon list. Each element of the list is a list or record produced as a by-product of a 3D output primitive (either a 3D function call, or an attribute that was set) written on that window. Unfortunately, the elements of the display lists are somewhat underdocumented at presents, so we will describe them in detail here.

Display Lists blindfolded

L := WindowContents(w)
every i := 1 to *L do {
   writes(i, ": ", image(L[i]), " -> ")
   every j := 1 to *(L[i]) do writes(image(L[i, j]), " ")
   write
   }

Display Lists with the headlights on

Flaws in the current Display List abstraction

Extending Texture(w, x) to Texture(w, x₁, x₂)

We will run out of texture memory sooner or later, but it needs to be later.

tex := Texture(w, s)
...
Texture(w, s, tex)

How soon? Well, I put the prototype code into ~jeffery/unicon/unicon last night, but it isn't tested or checked out on Windows yet. I'll try for ASAP.

Working in AlphaWorld (Churchhill chapter 15)

• Goal: use a off-the-shelf CVE for work collaborations instead of pure social.
• AlphaWorld vs. Blaxxun: AW less flexible, less visually appealing, but Blaxxun (VRML based) had problems: special/weird browser, poor performance... AW was a much smaller/faster browser.
• Reason voice chat is so important is so you can talk and "work" (i.e. type) at the same time. With text chat you have a major task- and window- switching issue.
• A Major feature of AW: extensibility
• Participatory Design: users and designers (of content) are one and the same. Who gets write permission? How easy is it to report a bug or request a change?

Lessons from Blaxxun

• spatial properties not used after initial exploration
• objects were not designed/built by users, had nothing to do with their topics of interest. No reason to interact with the world.
• lack of access to documents, no screen space available for other windows, led to a deficiency of content needed for collaborations.
• lack of privacy
• passers-by would hurl verbal abuse during business meetings!

Lessons from AW

• Sheer size allows for privacy: uninvited do not just happen by
• land-claim metaphor; you stake out 2D land before building in 3D on it
• Build tool integrated into regular viewing client, not a separate tool.
• Building your own space is a huge value-add for collaboration, mainly if you can populate it with useful content, e.g. URL's.
• AW was used in conjunction with BSCW.
• Easily implementable 3 grades of accessibility a la UNIX (ugo)
• Using stable public technology makes a project open -- they don't have to maintain the servers, accounts, etc.
• Individual ownership of objects was central in text-based MOO's but lost/dropped in many 3D CVE's.
• Build-by-copying. You can't create new objects, but you can copy and then modify existing objects.
• Clicking on or bumping into 3D objects "scriptable" with user-defined response (e.g. pulling up a webpage).
• Informal "chance encounters" are not chance at all, they are people we half-expect to meet, and benefit from meeting occasionally.
• AlphaWorld-based document navigation better than BSCW text interface; 3D navigation benefits scalability of file system access?!
• Creation of memory of the space came from using the space daily.
• Ease with which users can add their own rooms is crucial to a CVE's success
• Frontier Hypothesis - plentiful land waiting to be settled
• "New World Times" - server problems? A "giant meteor crashed into the virtual world, destroying everything..."
• Dr. J idea: give users disk space proportional to time spent in the CVE for customization.
• Value of the CVE to your friends depends on your being there a lot.

Resource Management

Singhal/Zyda assert that it is the Net resources that comprises the "cornerstone" of Networked Virtual Environments. All of the resource management in a NVE can be viewed in an information-centric way. The resource utilization for any category is: how much information is that resource using/processing.

Network-Centric View

Resources = M x H x B x T x P, where
M = Messages,
H = Hosts (destinations/message),
B = Bandwidth (bytes/message),
T = Timeliness (1/latency),
P = Processor (cycles/message)

Resource Tradeoff Techniques

Compression

lossless vs lossy, internal vs external

Packet aggregation

Can reduce bandwidth up to 50% at a cost of worse timeliness. Compare timeout vs. quorum vs. hybrid approaches to packet aggregation. Aggregation servers: might be organized by physical lan, msg type, teams, region

Visibility of Data

Area of interest filters, subscription-based, multicasting. Aura-nimbus approach allegedly performed poorly in MASSIVE

Level of Detail

Far away = small inaccuracies invisible

Server Clusters

CPU bottleneck or network bottleneck? client (group) partitioning, or region/zone partitioning

A Component Framework

A Unified Component Framework for Dynamically Extensible Virtual Environments

• From the "America's Army" game team at NPS
• NPSNET-V, fifth generation multiuser network game architecture?
• Java/XML, XML mainly for serialization that resists version conflicts
• upgrade components at runtime, never bring system down
• everything is upgradable except for a small "microkernel"
• strict hierarchical containment resembling file system directories
• "most important pattern" = Model-View-Controller
• Other projects: Bamboo (VR98, multilanguage multiplatform pluggable VE), JADE (Java Adaptive Dynamic Environment),
• replace() and retire() methods: cooperative handshake between old and new versions of a component

A bit more on Model-View-Controller

• Model: contains the state
• View: depicts the state to the user
• Controller: modifies the state

Downsides: three mirrored class graphs, instead of one; the "model" class is potentially all representation w/little behavior

Cursive: Controlling Avatar Gesture Using Pen Gesture

• (handwritten) mouse/pen gesture translated into avatar gesture
• separate symbolic and expressive parts of gesture
• user picks from a fixed set of gestures (symbols), but gets to convey expressiveness, e.g. via speed, size, or slant, of character (or if you had a tablet device, the pressure of the pen on it).
• How easy would it be to do a trivial version of this? What about other, lower-level gesture mechanisms? How many avatar gestures would be useful in our app?

• use fairly small patch of window in an "avatar area"
• base purely on press-drag*-release sequences in that area
• "size" based on pythagoras equation on the bounding box
• "speed" based on sum of &interval times (could use sequence of &intervals)
• want a few gestures, without a full handwriting recognition package
• compare w/ Palm pilot Graffiti: a simplified symbol set
• raise hand, lower hand, smile, shrug, etc.

Opening Comic

Things Our CVE Needs "Real Bad"

• more server state; server keeping track, e.g. of door states, blackboard states, user states; backing this up on disk
• network commands that provide ability to transmit (efficiently) blackboard contents and changes to server and thence to interested clients.

In Class n-User CVE Demo

• The server is too fragile. The VM code to handle lost connections appears to have a bug. In addition the VM on the client should probably be extended to close network connections on program termination, apparently just calling exit() is not very friendly.
• Some avatars' heads look much better than others (Gustav and Yo, for example. The difference is not original resolution in pixels, but rather, a solid background allowed more colors for the actual face. Adding JPEG support for textures, or using a 24-bit BMP format, would fix this without having to edit/redo the images manually.
• Performance - I couldn't tell whether the network or the server limited client performance; we won't know until the clients' performance and user interface have been tuned. It was OK with 5.

Q: Why and for what, do we need file transfers?
A: User-supplied textures. New data and code files. Patching the executable.

Features We Need to Integrate

• blackboard/whiteboard
• configuration files (config GUI screen)
• map window
• groups
• accounts/passwords
• user state
• VOICE - www.cs.nmsu.edu
• texture objects
• API support for manipulating the display list
• API support for manipulating the event pending list

Features We Need to do Starting From Scratch

• patcher
• file transfer
• corridors
• document sharing
• MIME types - fire off external programs
• transmit avatars @ runtime

Features we Wish we Could Do, But not Anytime Soon

• room builder/ room decorator
• ghost (or multi) avatars
• much better avatars
• Icons for education - assignments, labs, exams, discussions

Links of Interest

• Game Optimization
• 15 Tips for Finishing a Game

Miscellany on other Genres

RPG's

Role Playing is some stupid exercise used by psychologists and counselors to try to get people to see situations from different points of view. But Role Playing Games starting with Dungeons and Dragons applied that basic technique to imaginative first-person gaming.

Example Pencil-and-Paper RPG's

• Dungeons and Dragons, Tunnels and Trolls, Bunnies and Burrows...
• Micro-RPG's (Melee, Wizard)
• Traveller (SCI-FI), and Shadowrun (Cyberpunk)
• Vampire the Masquerade, and other monster-genres

Example PC-based RPG's

• Rogue, hack, nethack, moria
• Diablo
• Icewind Dale, Neverwinter Nights

Educational Games and Serious Games

• Science Pirates
• Video: How to make Educational Games that Don't Stink