来点真正的3D

<div class="page-header"><h3>4、来点真正的3D</h3></div>

<canvas id = "test04-canvas" width = "800" height = "600"></canvas>

<script id = "shader-vs" type = "x-shader/x-vertex">
    attribute vec3 aVertexPosition;
    attribute vec4 aVertexColor;
    uniform mat4 uMVMatrix;
    uniform mat4 uPMatrix;
    varying vec4 vColor;
    void main(void)
    {
        gl_Position = uPMatrix * uMVMatrix * vec4(aVertexPosition, 1.0);
        vColor = aVertexColor;
    }
</script>

<script id = "shader-fs" type = "x-shader/x-fragment">
    precision mediump float;

    varying vec4 vColor;

    void main(void)
    {
        gl_FragColor = vColor;
    }
</script>
<script type="text/javascript">
    requestAnimFrame = window.requestAnimationFrame ||
        window.mozRequestAnimationFrame ||
        window.webkitRequestAnimationFrame ||
        window.msRequestAnimationFrame ||
        window.oRequestAnimationFrame ||
        function(callback) { setTimeout(callback, 1000 / 60); };
</script>
<script type="text/javascript">

$(document).ready(function ()
{
    webGLStart();
});

function webGLStart()
{
    var canvas = $("#test04-canvas")[0];
    initGL(canvas);
    initShaders();
    initBuffers();

    gl.clearColor(0.0, 0.0, 0.0, 1.0);
    gl.enable(gl.DEPTH_TEST);

//     drawScene();

    tick();
}

function tick()
{
    requestAnimFrame(tick);
    drawScene();
    animate();
}

var gl;
function initGL(canvas)
{
    try
    {
        gl = canvas.getContext("webgl") || canvas.getContext("experimental-webgl");
        gl.viewportWidth = canvas.width;
        gl.viewportHeight = canvas.height;
    }catch(e){}
    if(!gl)
    {
        alert("无法初始化“WebGL”。");
    }
}

function getShader(gl, id)
{
    var shaderScript = $("#" + id);
    if(!shaderScript.length)
    {
        return null;
    }
    var str = shaderScript.text();

    var shader;
    if(shaderScript[0].type == "x-shader/x-fragment")
    {
        shader = gl.createShader(gl.FRAGMENT_SHADER);
    }
    else if(shaderScript[0].type == "x-shader/x-vertex")
    {
        shader = gl.createShader(gl.VERTEX_SHADER);
    }
    else
    {
        return null;
    }
    gl.shaderSource(shader, str);
    gl.compileShader(shader);
    if(!gl.getShaderParameter(shader, gl.COMPILE_STATUS))
    {
        alert(gl.getShaderInfoLog(shader));
        return null;
    }
    return shader;
}

var shaderProgram;
function initShaders()
{
    var fragmentShader = getShader(gl, "shader-fs");
    var vertexShader = getShader(gl, "shader-vs");
    shaderProgram = gl.createProgram();
    gl.attachShader(shaderProgram, vertexShader);
    gl.attachShader(shaderProgram, fragmentShader);
    gl.linkProgram(shaderProgram);

    if(!gl.getProgramParameter(shaderProgram, gl.LINK_STATUS))
    {
        alert("无法初始化“Shader”。");
    }
    gl.useProgram(shaderProgram);

    shaderProgram.vertexPositionAttribute =
        gl.getAttribLocation(shaderProgram, "aVertexPosition");
    gl.enableVertexAttribArray(shaderProgram.vertexPositionAttribute);

    shaderProgram.vertexColorAttribute =
        gl.getAttribLocation(shaderProgram, "aVertexColor");
    gl.enableVertexAttribArray(shaderProgram.vertexColorAttribute);

    shaderProgram.pMatrixUniform =
        gl.getUniformLocation(shaderProgram, "uPMatrix");
    shaderProgram.mvMatrixUniform =
        gl.getUniformLocation(shaderProgram, "uMVMatrix");
}


var mvMatrix = mat4.create();

var mvMatrixStack = [];

var pMatrix = mat4.create();

function mvPushMatrix()
{
    var copy = mat4.clone(mvMatrix);
    mvMatrixStack.push(copy);
}
function mvPopMatrix()
{
    if(mvMatrixStack.length == 0)
    {
        throw "不合法的矩阵出栈操作!";
    }
    mvMatrix = mvMatrixStack.pop();
}

function setMatrixUniforms()
{
    gl.uniformMatrix4fv(shaderProgram.pMatrixUniform, false, pMatrix);
    gl.uniformMatrix4fv(shaderProgram.mvMatrixUniform, false, mvMatrix);
}


var pyramidVertexPositionBuffer;
var pyramidVertexColorBuffer;
var cubeVertexPositionBuffer;
var cubeVertexColorBuffer;
var cubeVertexIndexBuffer;

function initBuffers()
{
    pyramidVertexPositionBuffer = gl.createBuffer();
    gl.bindBuffer(gl.ARRAY_BUFFER, pyramidVertexPositionBuffer);
    var vertices = [
                    // 正面
                     0.0, 1.0, 0.0,
                    -1.0, -1.0, 1.0,
                     1.0, -1.0, 1.0,
                    // 右侧面
                     0.0, 1.0, 0.0,
                     1.0, -1.0, 1.0,
                     1.0, -1.0, -1.0,
                    // 背面
                     0.0, 1.0, 0.0,
                     1.0, -1.0, -1.0,
                    -1.0, -1.0, -1.0,
                    // 左侧面
                     0.0, 1.0, 0.0,
                    -1.0, -1.0, -1.0,
                    -1.0, -1.0, 1.0
                    ];
    gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices),
        gl.STATIC_DRAW);
    pyramidVertexPositionBuffer.itemSize = 3;
    pyramidVertexPositionBuffer.numItems = 12;

    pyramidVertexColorBuffer = gl.createBuffer();
    gl.bindBuffer(gl.ARRAY_BUFFER, pyramidVertexColorBuffer);
    var colors = [
                 // 正面
                 1.0, 0.0, 0.0, 1.0,
                 0.0, 1.0, 0.0, 1.0,
                 0.0, 0.0, 1.0, 1.0,
                 // 右侧面
                 1.0, 0.0, 0.0, 1.0,
                 0.0, 0.0, 1.0, 1.0,
                 0.0, 1.0, 0.0, 1.0,
                 // 背面
                 1.0, 0.0, 0.0, 1.0,
                 0.0, 1.0, 0.0, 1.0,
                 0.0, 0.0, 1.0, 1.0,
                 // 左侧面
                 1.0, 0.0, 0.0, 1.0,
                 0.0, 0.0, 1.0, 1.0,
                 0.0, 1.0, 0.0, 1.0
                ];
     gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(colors),
         gl.STATIC_DRAW);
     pyramidVertexColorBuffer.itemSize = 4;
     pyramidVertexColorBuffer.numItems = 12;


    cubeVertexPositionBuffer = gl.createBuffer();
    gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexPositionBuffer);
    vertices = [
                // 正面
                -1.0, -1.0,  1.0,
                 1.0, -1.0,  1.0,
                 1.0,  1.0,  1.0,
                -1.0,  1.0,  1.0,

                // 背面
                -1.0, -1.0, -1.0,
                -1.0,  1.0, -1.0,
                 1.0,  1.0, -1.0,
                 1.0, -1.0, -1.0,

                // 顶部
                -1.0,  1.0, -1.0,
                -1.0,  1.0,  1.0,
                 1.0,  1.0,  1.0,
                 1.0,  1.0, -1.0,

                // 底部
                -1.0, -1.0, -1.0,
                 1.0, -1.0, -1.0,
                 1.0, -1.0,  1.0,
                -1.0, -1.0,  1.0,

                // 右侧面
                 1.0, -1.0, -1.0,
                 1.0,  1.0, -1.0,
                 1.0,  1.0,  1.0,
                 1.0, -1.0,  1.0,

                // 左侧面
                -1.0, -1.0, -1.0,
                -1.0, -1.0,  1.0,
                -1.0,  1.0,  1.0,
                -1.0,  1.0, -1.0,
                ];
    gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices),
        gl.STATIC_DRAW);
    cubeVertexPositionBuffer.itemSize = 3;
    cubeVertexPositionBuffer.numItems = 24;

    cubeVertexColorBuffer = gl.createBuffer();
    gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexColorBuffer);
    colors = [
              [1.0, 0.0, 0.0, 1.0],     // 正面
              [1.0, 1.0, 0.0, 1.0],     // 背面
              [0.0, 1.0, 0.0, 1.0],     // 顶部
              [1.0, 0.5, 0.5, 1.0],     // 底部
              [1.0, 0.0, 1.0, 1.0],     // 右侧面
              [0.0, 0.0, 1.0, 1.0]     // 左侧面
            ];
    var unpackedColors = [];
    for (var i in colors)
    {
        var color = colors[i];
        for (var j=0; j < 4; j++)
        {
            unpackedColors = unpackedColors.concat(color);
        }
    }
    gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(unpackedColors),
        gl.STATIC_DRAW);
    cubeVertexColorBuffer.itemSize = 4;
    cubeVertexColorBuffer.numItems = 24;

    cubeVertexIndexBuffer = gl.createBuffer();
    gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, cubeVertexIndexBuffer);
    var cubeVertexIndices = 
        [
          0, 1, 2,      0, 2, 3,    // 正面
          4, 5, 6,      4, 6, 7,    // 背面
          8, 9, 10,     8, 10, 11,  // 顶部
          12, 13, 14,   12, 14, 15, // 底部
          16, 17, 18,   16, 18, 19, // 右侧面
          20, 21, 22,   20, 22, 23  // 左侧面
        ];
    gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, 
        new Uint16Array(cubeVertexIndices), gl.STATIC_DRAW);
    cubeVertexIndexBuffer.itemSize = 1;
    cubeVertexIndexBuffer.numItems = 36;
}

var rPyramid = 0;
var rCube = 0;
function drawScene()
{
    gl.viewport(0, 0, gl.viewportWidth, gl.viewportHeight);
    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

    mat4.perspective(pMatrix, 45, gl.viewportWidth /
        gl.viewportHeight, 0.1, 100.0);

    mat4.identity(mvMatrix);

    mat4.translate(mvMatrix, mvMatrix, [-1.5, 0.0, -8.0]);

    mvPushMatrix();
    mat4.rotate(mvMatrix, mvMatrix, degToRad(rPyramid), [0, 1, 0]);

    gl.bindBuffer(gl.ARRAY_BUFFER, pyramidVertexPositionBuffer);
    gl.vertexAttribPointer(shaderProgram.vertexPositionAttribute,
        pyramidVertexPositionBuffer.itemSize, gl.FLOAT, false, 0, 0);

    gl.bindBuffer(gl.ARRAY_BUFFER, pyramidVertexColorBuffer);
    gl.vertexAttribPointer(shaderProgram.vertexColorAttribute,
        pyramidVertexColorBuffer.itemSize, gl.FLOAT, false, 0, 0);

    setMatrixUniforms();
    gl.drawArrays(gl.TRIANGLES, 0,
        pyramidVertexPositionBuffer.numItems);

    mvPopMatrix();

    mat4.translate(mvMatrix, mvMatrix, [ 3.0, 0.0, 0.0]);

    mvPushMatrix();
    mat4.rotate(mvMatrix, mvMatrix, degToRad(rCube), [1, 1, 1]);

    gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexPositionBuffer);
    gl.vertexAttribPointer(shaderProgram.vertexPositionAttribute,
        cubeVertexPositionBuffer.itemSize, gl.FLOAT, false, 0, 0);

    gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexColorBuffer);
    gl.vertexAttribPointer(shaderProgram.vertexColorAttribute,
        cubeVertexColorBuffer.itemSize, gl.FLOAT, false, 0, 0);

    gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, cubeVertexIndexBuffer);
    setMatrixUniforms();
    gl.drawElements(gl.TRIANGLES,
        cubeVertexIndexBuffer.numItems, gl.UNSIGNED_SHORT, 0);

    mvPopMatrix();
}
function degToRad(degrees)
{
    return degrees * Math.PI / 180;
}
var lastTime = 0;
function animate()
{
    var timeNow = new Date().getTime();
    if(lastTime != 0)
    {
        var elapsed = timeNow - lastTime;

        rPyramid += (90 * elapsed) / 1000.0;
        rCube += (75 * elapsed) / 1000.0;
    }
    lastTime = timeNow;
}
</script>