Loading [MathJax]/extensions/tex2jax.js

2014年9月15日月曜日

少しましなWebGLサンプル

はじめてのWebGLのサンプルはindex.htmlにGLSLもJavaScriptもすべて詰め込んでしまっていたので、GLSLをHTMLに書いて、JavaScriptは切り分けるように書き直した。webgl-debug.jsはDebugging - WebGL Public Wikiの物を使えばいいです。
<html>
<head>
<title>WebGL</title>
<script src="script.js" type="text/javascript"></script>
<script src="webgl-debug.js" type="text/javascript"></script>
<script id="shader-vs" type="x-shader/x-vertex">
attribute vec3 aVertexPosition;
void main(){
gl_Position = vec4(aVertexPosition, 1.0);
}
</script>
<script id="shader-fs" type="x-shader/x-fragment">
precision mediump float;
void main(){
gl_FragColor = vec4(1.0,1.0,1.0,1.0);
}
</script>
</head>
<body onload="startup();">
<canvas id="myGLCanvas" width="500" height="500"></canvas>
</body>
</html>
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var gl;
var canvas;
var shaderProgram;
var vertexBuffer;
function createGLContext(canvas){
var context = null;
context = canvas.getContext("webgl");
if(context){
context.viewportWidth = canvas.width;
context.viewportHeight = canvas.height;
} else {
alert("Failed to create WebGL context");
}
return context;
}
function loadShaderFromDOM(id){
var shaderScript = document.getElementById(id);
if(!shaderScript){
return null;
}
var shaderSource = "";
var currentChild = shaderScript.firstChild;
while(currentChild){
if(currentChild.nodeType == 3){
shaderSource += currentChild.textContent;
}
currentChild = currentChild.nextSibling;
}
var shader;
if(shaderScript.type == "x-shader/x-fragment"){
shader = gl.createShader(gl.FRAGMENT_SHADER);
}else if(shaderScript.type == "x-shader/x-vertex"){
shader = gl.createShader(gl.VERTEX_SHADER);
}else{
return null;
}
gl.shaderSource(shader,shaderSource);
gl.compileShader(shader);
if(!gl.getShaderParameter(shader,gl.COMPILE_STATUS)){
alert("Error compiling shader " + gl.getShaderInfoLog(shader));
return null;
}
return shader;
}
function setupShaders(){
var vertexShader = loadShaderFromDOM("shader-vs");
var fragmentShader = loadShaderFromDOM("shader-fs");
shaderProgram = gl.createProgram();
gl.attachShader(shaderProgram,vertexShader);
gl.attachShader(shaderProgram,fragmentShader);
gl.linkProgram(shaderProgram);
if(!gl.getProgramParameter(shaderProgram,gl.LINK_STATUS)){
alert("Failed to setup shaders");
}
gl.useProgram(shaderProgram);
shaderProgram.vertexPositionAttribute = gl.getAttribLocation(shaderProgram,"aVertexPosition");
}
function setupBuffers(){
vertexBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);
var triangleVertices = [
0.0, 0.5, 0.0,
-0.5,-0.5, 0.0,
0.5,-0.5, 0.0
];
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(triangleVertices),gl.STATIC_DRAW);
vertexBuffer.itemSize = 3;
vertexBuffer.numberOfItems = 3;
}
function draw() {
gl.viewport(0,0,gl.viewportWidth,gl.viewportHeight);
gl.clear(gl.COLOR_BUFFER_BIT);
gl.vertexAttribPointer(shaderProgram.vertexPositionAttribute,vertexBuffer.itemSize, gl.FLOAT, false, 0, 0);
gl.enableVertexAttribArray(shaderProgram.vertexPositionAttribute);
gl.drawArrays(gl.TRIANGLES,0,vertexBuffer.numberOfItems);
}
function startup(){
canvas = document.getElementById("myGLCanvas");
gl = createGLContext(canvas);
if(window.WebGLDebugUtils){
gl = WebGLDebugUtils.makeDebugContext(gl);
}
setupShaders();
setupBuffers();
gl.clearColor(0.0,0.0,0.0,1.0);
draw();
}
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