Introduction to WebGL and Three.js

Introduction to WebGL and Three.js

James Williams

James.L.Williams@gmail.com - Rearden Commerce

About Me
• Author of Learning HTML5
Game Programming
• Google+: +JamesWilliams
• Twitter: @ecspike
• http://jameswilliams.be/blog

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James.L.Williams@gmail.com – Rearden Commerce

Agenda - WebGL
• What are WebGL and Three.js?
• Lighting, Shaders, and Materials
• Creating Meshes
• GLSL
• Animation
• Debugging
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What is WebGL?
• Low-level 3D graphics context
• Hardware accelerated
• Supported by most modern browsers
• Syntax is based on OpenGL ES 2.0

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Getting a WebGLContext
• Hook to draw on the canvas
var canvas = document.getElementById(“c”);
var ctx = c.getContext(“experimental-webgl”);

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What is Three.js?
• Abstraction layer over WebGL
• 3D scenegraph library
• Capable of rendering to
– Canvas2D, WebGL, or SVG
• Exporters for popular 3D formats
• http://github.com/mrdoob/three.js

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Initializing Three.js
function init() {
var HEIGHT = 480, WIDTH = 640;
// create a renderer, camera, and scene
renderer = new THREE.WebGLRenderer();
renderer.setSize (WIDTH, HEIGHT);
camera = /* truncated */
// create scene
scene = new THREE.Scene();
// add objects to scene
elem.appendChild(render.domElement);
}
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Camera
• Eye point
• Field of vision
• Near / Far planes
• Target(LookAt) point
• Up vector
• Advanced Camera types
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Creating Meshes
• Geometry vs Mesh
• Built-in geometries
• Vertex
new THREE.Vertex(
new Three.Vector3(0.0, 1.0, 0.0)
);
• Face
new THREE.Face3(0,1,2);

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Creating Meshes
geometry = new THREE.Geometry();
geometry.vertices.push(vertex1);
geometry.faces.push(face1);
var triangle = new THREE.Mesh(geometry,
new THREE.MeshBasicMaterial( {
color: 0x00ff00 }
)
);

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Creating Meshes
plane = new THREE.Mesh(
new THREE.PlaneGeometry( 200, 200 ),
new THREE.MeshBasicMaterial( { color:
0xe0e0e0 }
)
);
scene.add( plane );
scene.add(triangle);

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Demo

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Lighting
• Ambient
• Point
• Directional
• SpotLight
new THREE.AmbientLight(hexColor);
new THREE.PointLight(hexColor, [intensity], [distance]);

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Shading
• Flat
• Lambertian
• Gouraud
• Phong

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Materials
• MeshBasicMaterial
• MeshLambertMaterial
• MeshPhongMaterial
• MeshShaderMaterial

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Demo

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Texturing
• Can load from images or use canvas data
• Basic shapes precalculate texture coordinates

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2D Texture Coordinates
(0,0) (1,1)

(0,1) (1,0)
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Texturing Example
var texture = THREE.ImageUtils.loadTexture(
"200407-bluemarble.jpg" );
var material = new THREE.MeshBasicMaterial(
{ color: 0xFFFFFF,
ambient: 0xFFFFFF, map:texture } );

sphere = new THREE.Mesh(
new THREE.SphereGeometry(32, 32, 32), material
);

scene.add(sphere);
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Demo

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Loading Models
function drawCube() {
var loader = new THREE.JSONLoader();
loader.load( {model: "cube.js", callback: createScene1 });
}

function createScene1(obj) {
obj.materials[0][0].shading = THREE.FlatShading;
mesh = THREE.SceneUtils.addMesh( scene, obj, 250, 400, 0,
0, 0, 0, 0,obj.materials[0] );
}

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Demo

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What is GLSL?
• High-level language with C-like syntax
• Targets the GPU and graphics pipeline
• A GLSL program consists of
– fragment shader
– vertex shader
• Content of shaders passed around as strings
• Shaders can be generated at run-time
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Vertex Shaders
• Run once per vertex in a mesh
• Can alter color, position, texels, etc at that
vertex

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Example Vertex Shader
<script id="shader-vs" type="x-shader/x-vertex">
void main(void) {
gl_Position = projectionMatrix *
modelViewMatrix *
vec4(position, 1.0);
}
</script>

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Fragment(Pixel) Shaders
• Run once per pixel in a mesh
• Can produce effects such as bump and env
mapping

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Example Fragment(Pixel) Shader
<script id="shader-vs" type="x-shader/x-fragment">
void main(void) {
gl_FragColor = vec4(
0.0, 1.0, 0.0, 1.0
);
}
</script>

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Shader Demo Code
shaderMaterial = new
THREE.MeshShaderMaterial({
vertexShader: $('#v').get(0).innerHTML,
fragmentShader:$('#f').get(0).innerHTML,
vertexColors: true
});
/* truncated */
var triangle = new THREE.Mesh(
geometry, shaderMaterial
);

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Shader Variables
• uniform
• varying
• attribute
• Types

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Constructing New Shader Types
struct MyMaterial {
vec4 ambient;
vec4 diffuse;
vec4 specular;
float shininess;
};

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Communicating with Shaders
var uniforms;
uniforms = {
time: {type:"f", value:0.0}
}
shaderMaterial = new THREE.MeshShaderMaterial({
uniforms: uniforms,
vertexShader:$('#v').get(0).innerHTML,
fragmentShader:$('#f').get(0).innerHTML,
});

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Custom Shader
uniform float time;

void main(){
float r = cos(time);
float g = sin(time);
float b = tan(time);

gl_FragColor = vec4(r, 1.0 - g , b, 1.0);
}

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Vertex Shader for 2D texturing
/* Vertex Shader */
attribute vec4 a_position;
attribute vec2 a_texCoord;
varying vec2 v_texCoord;

void main() {
gl_Position = a_position;
v_texCoord = a_texCoord;
}

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Fragment Shader for 2D texturing
/* Fragment Shader */
precision mediump float;
varying vec2 v_texCoord;
uniform sampler2D s_texture;

void main() {
gl_FragColor = texture2D(s_texture, v_texCoord);
}

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Animation
Armature - 3D representation of bones, ligaments, and
tendons
• Forward kinematics
• Inverse kinematics
• Keyframes/Morph targets

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MorphTargets
var time = new Date().getTime() % duration;
var keyframe = Math.floor(time / interpol )
+ offset;
if ( keyframe != currentKeyframe ) {
mesh.morphTargetInfluences[lastFrame]=0;
mesh.morphTargetInfluences[currentFrame]
=1;
mesh.morphTargetInfluences[keyframe]=0;
lastFrame = currentFrame;
currentFrame = keyframe;
}

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MorphTargets
mesh.morphTargetInfluences[ keyframe ]
= ( time % interpol ) / interpolation;

mesh.morphTargetInfluences[ lastFrame ]
= 1 - mesh.morphTargetInfluences[keyframe];

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Demo

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Debugging WebGL

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Stats.js
• Measures:
– FPS - frames per second
– MS - millis to render frame
– MB - allocated MB
• Github:https://github.com/mrdoob/stats.js

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Stats.js code
var stats = new Stats()
$("body").append(stats.domElement);

//... in your render function
stats.update();

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WebGL Inspector
• Allows you to step through rendering
• View assets and programs
• Capture individual frames
• Github: http://benvanik.github.com/WebGL-Inspector

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Questions?

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Introduction to WebGL and Three.js

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Introduction to WebGL and Three.js

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