<!doctype html>
<html>
<head>
<meta charset="UTF-8">
<meta name="viewport"
content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
<style>
body {
margin: 0;
text-align: center;
}
#canvas {
margin: 0;
}
</style>
</head>
<body onload="main()">
<canvas id="canvas" height="800" width="800">
你的浏览器不支持WebGL，请更换新的浏览器
</canvas>
</body>
<script src="/lib/webgl-utils.js"></script>
<script src="/lib/webgl-debug.js"></script>
<script src="/lib/cuon-utils.js"></script>
<script src="/lib/cuon-matrix.js"></script>
<script>
//顶点着色器
var VSHADER_SOURCE = "" +
"attribute vec4 a_Position;\n" +
"attribute vec4 a_Color;\n" +
"varying vec4 v_Color;\n" +//声明varying类型的变量
"void main(){\n" +
" gl_Position = a_Position;\n" +
" gl_PointSize = 10.0;\n" +
" v_Color = a_Color;\n" +//将数据传给片元着色器
"}\n";
//片元着色器
var FSHADER_SOURCE = "" +
"precision mediump float;\n" +//!!! 需要声明浮点数精度，否则报错No precision specified for (float)
"varying vec4 v_Color;\n" +//在片元着色器里面使用varying声明相同的变量
"void main(){\n" +
" gl_FragColor = v_Color;\n" +//将变量赋值给颜色
"}\n";
//加载完成调用的方法
function main() {
var canvas = document.getElementById("canvas");
var gl = getWebGLContext(canvas);
if(!gl){
console.log("电脑不支持WebGL");
return;
}
if(!initShaders(gl,VSHADER_SOURCE,FSHADER_SOURCE)){
console.log("初始化着色器失败");
return;
}
var n = initVertexBuffers(gl);
gl.clearColor(0.0,0.0,0.0,1.0);
gl.clear(gl.COLOR_BUFFER_BIT);
gl.drawArrays(gl.TRIANGLES,0,n);
}
function initVertexBuffers(gl) {
//顶点坐标和点的尺寸
var verticesSizes = new Float32Array([
0.0,0.5,1.0,0.0,0.0,//第一个点
-0.5,-0.5,0.0,1.0,0.0,//第二个点
0.5,-0.5,0.0,0.0,1.0//第三个点
]);
var n = 3;
//创建缓冲区
var vertexSizeBuffer = gl.createBuffer();
if(!vertexSizeBuffer){
console.log("无法创建缓冲区对象");
return -1;
}
//将顶点坐标和尺寸写入缓冲区并开启
gl.bindBuffer(gl.ARRAY_BUFFER,vertexSizeBuffer);
gl.bufferData(gl.ARRAY_BUFFER,verticesSizes,gl.STATIC_DRAW);
//获取Float32Array中每个元素所占的字节数
var FSIZE = verticesSizes.BYTES_PER_ELEMENT;
//获取a_Position的存储位置，分配缓冲区并开启
var a_Position = gl.getAttribLocation(gl.program,"a_Position");
if(a_Position < 0){
console.log("无法获取顶点的存储位置");
return;
}
//对位置进行分配
gl.vertexAttribPointer(a_Position,2,gl.FLOAT,false,FSIZE*5,0);
//开启分配
gl.enableVertexAttribArray(a_Position);
//获取a_PointSize的存储位置
var a_Color = gl.getAttribLocation(gl.program,"a_Color");
if(a_Color < 0){
console.log("无法获取顶点尺寸的变量的存储位置");
return;
}
//对位置进行分配
gl.vertexAttribPointer(a_Color,3,gl.FLOAT,false,FSIZE*5,FSIZE*2);
//开启分配
gl.enableVertexAttribArray(a_Color);
return n;
}
</script>
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