<games /><games />

Gil Megidishgil@megidish.net

And I love writing / rewriting / reverse engineering games

Canvas

Video

Audio

Web Sockets

Web Storage

Web Worker

Web Database

Selectors

Validation

File API

Semantic Elements

What The Heck is HTML5

Games + Javascript?= wtf

Why Bother With Javascript?• Fun to develop

– Hacker’s spielplatz!

• Fast deployment– Serve static files

• Easy to debug– alert(), firebug.. Still better than the alternative!

• Open source and free tools– Notepad, vi, emacs

• B.Y.O. framework– jQuery?

spielplatz

But Why REALLY?

• Has been around for ages• Won’t go away any time soon

• Wide support:– Web browsers– Mobile devices– Facebook applications– On a rocket near you

LOGIC

GRAPHICS

INPUT

SOUND

Anatomy of a Game

MUSIC

MULTIPLAYER

GAME ASSETS

LOGIC

GRAPHICS

INPUT

SOUND

Anatomy of a Game

MUSIC

MULTIPLAYER

GAME ASSETS

javascript code

<canvas>

onkeydown, onmousedown

<audio>

<audio>

ajax, WebSocket

Images, Audio, Video and Binary supported by browsers

Graphics

Framebuffer (raw)

0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,x

1,0 1,1 1,2 1,3 1,4 1,5 1,6 1,7 1,x

y,0 y,1 y,2 y,3 y,4 y,5 y,6 y,7 y,x

x

y…

…

…

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Tile + Sprite Memory

Scene Graph

Placeholder For Future Presentation

Canvas is KingCanvas is King

DEMO TIME!

Three Demos To Rule Them All

Framebuffer demo

http://www.megidish.net/apple2js/

Sprites demo

http://www.megidish.net/alphageeks6/luigi/

Vector graphics demo

http://www.megidish.net/awjs/

Catch me a canvas

<canvas id=“graphics” width=“640” height=“480”>Guru Meditation: No canvas supported!

</canvas>

var canvas = document.getElementById(“graphics”);var context = canvas.getContext(“2d”);

Drawing Primitives

ctx.fillStyle = “#c80000"; ctx.fillRect (10, 10, 55, 50);

ctx.fillStyle = "rgba(0, 0, 200, 0.5)"; ctx.fillRect (30, 30, 55, 50);

Other drawing methods: arc, bezierCurve, lineTo, quadraticCurve, rect, stroke, fillText, strokeText, beginPath/closePath and fill

(but who needs that ?)

Drawing Images

var sprite = new Image();sprite.src = “luigi.png”;

var x = 0, y = 0;ctx.drawImage(sprite, x, y);

Drawing Images 2var spritemap = new Image();spritemap.src = “sprite-map.png”;

ctx.drawImage(spritemap,sx, sy,sw, sh,dx, dy,dw, dh

);

Sprite maps save loading time by fewer requests and better compression. drawImage() also provides scaling and cropping.

Going Crazy With Images

// context state checkpointctx.save();

ctx.translate(0, 80);ctx.rotate(-45 * Math.PI / 180.0);ctx.scale(3.0, 1.0);ctx.drawImage(luigi, 0, 0);

// revert all context changesctx.restore();

Accessing Pixels

var block = ctx.getImageData(sx, sy, sw, sh);block = {

width: width in pixels,height: height in pixels,data: array of 4*width*height bytes

};

Alternatively: ctx.createImageData(w, h);

Accessing Pixels

var block = ctx.getImageData(0, 0, canvas.width/2, canvas.height);for (var y=0; y<block.height; y++) {

for (var x=0; x<block.width; x++) {

block.data[(y*block.width+x)*4+0] ^= 0xff;block.data[(y*block.width+x)*4+1] ^= 0xff;block.data[(y*block.width+x)*4+2] ^= 0xff;

}}

ctx.putImageData(block, 0, 0);

Why Access Pixels ?

Complicated things impossible without putImageData()

Read image pixels getImageData combined with primitive drawing = save image to disk!

These examples are available to http://www.chromeexperiments.com/

The Jazz Singer

Let There Be Sound!

<audio id=“sfx001” src=“/mp3/boom.mp3”></audio>$(“sfx001”).play();

Let There Be Sound!

<audio id=“sfx001” src=“/mp3/boom.mp3”></audio>$(“sfx001”).play();

Other methods:$(“sfx001”).pause();

Other attributes:$(“sfx001”).currentTime = 35.0;$(“sfx001”).volume = 0.5; $(“sfx001”).duration (read only)

Putting It All Together

Typical Game Loop

function gameTick(){

processKeyboard();moveEnemies();drawGraphics();updateAudio();

}

var fps = 60;setInterval(gameTick, 1000 / fps);

The Future is Upon Us!

Quake2 HTML5

What’s Coming Up Next• WebGL

– OpenGL interface for Javascript– As of May, 2010: good luck finding a stable browser!

• WebSocket– UDP and nonblocking transport layer – Not there yet! (KAAZING?)

• WebStorage– Save games?

Code Like It’s 2020!

ftw!‘s

Blackberry coming June 1st!

Q&A

Q&A

• Yes! You can use <canvas> in Internet Explorer 6?

<!--[if IE]><script type="text/javascript“ src="/js/excanvas.js"></script>

<![endif]-->

PS. Remember to upgrade your mother’s IE!

Links!

• Chrome Experiments: Not Your Momma’s JS– http://www.chromeexperiments.com

• Appcelerator’s Titanium– www.appcelerator.com

• Box 2D: real time physics for JS games– http://box2d-js.sourceforge.net/index2.html

• Mozilla’s Canvas tutorial– https://developer.mozilla.org/en/Canvas_tutorial

GO MAKE GAMES!GO MAKE GAMES!

http://www.megidish.net