引入纹理

<div class="page-header"><h3>5、引入纹理</h3></div>

<canvas id = "test05-canvas" width = "800" height = "600"></canvas>

<script id = "shader-vs" type = "x-shader/x-vertex">
    attribute vec3 aVertexPosition;
    attribute vec2 aTextureCoord;

    uniform mat4 uMVMatrix;
    uniform mat4 uPMatrix;

    varying vec2 vTextureCoord;
    void main(void)
    {
        gl_Position = uPMatrix * uMVMatrix * vec4(aVertexPosition, 1.0);
        vTextureCoord = aTextureCoord;
    }
</script>

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

    varying vec2 vTextureCoord;
    uniform sampler2D uSampler;

    void main(void)
    { 
        gl_FragColor =
            texture2D(uSampler, vec2(vTextureCoord.s, vTextureCoord.t));
    }
</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 = $("#test05-canvas")[0];
    initGL(canvas);
    initShaders();
    initBuffers();
    initTexture();

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

//    setTimeout("tick()", 100);
}
var myTexture;
function initTexture()
{
    myTexture = gl.createTexture();
    myTexture.image = new Image();
    myTexture.image.onload = function()
    {
        handleLoadedTexture(myTexture);
        tick();
    }
    myTexture.image.src = "/Public/image/mytexture.jpg";
}
function handleLoadedTexture(texture)
{
    gl.bindTexture(gl.TEXTURE_2D, texture);
    gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL, 1);
    gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA,
        gl.UNSIGNED_BYTE, texture.image);
    gl.texParameteri(gl.TEXTURE_2D,
        gl.TEXTURE_MAG_FILTER, gl.NEAREST);
    gl.texParameteri(gl.TEXTURE_2D,
        gl.TEXTURE_MIN_FILTER, gl.NEAREST);
    gl.bindTexture(gl.TEXTURE_2D, null);
}
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.textureCoordAttribute =
        gl.getAttribLocation(shaderProgram, "aTextureCoord");
    gl.enableVertexAttribArray(shaderProgram.textureCoordAttribute);

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


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 cubeVertexPositionBUffer;
var cubeVertexTextureCoordBuffer;
var cubeVertexIndexBuffer;

function initBuffers()
{
    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;

    cubeVertexTextureCoordBuffer = gl.createBuffer();
    gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexTextureCoordBuffer);
    textureCoords = [
                     // 正面
                     0.0, 0.0,
                     1.0, 0.0,
                     1.0, 1.0,
                     0.0, 1.0,

                     // 背面
                     1.0, 0.0,
                     1.0, 1.0,
                     0.0, 1.0,
                     0.0, 0.0,

                     // 顶部
                     0.0, 1.0,
                     0.0, 0.0,
                     1.0, 0.0,
                     1.0, 1.0,

                     // 底部
                     1.0, 1.0,
                     0.0, 1.0,
                     0.0, 0.0,
                     1.0, 0.0,

                     // 右侧面
                     1.0, 0.0,
                     1.0, 1.0,
                     0.0, 1.0,
                     0.0, 0.0,

                     // 左侧面
                     0.0, 0.0,
                     1.0, 0.0,
                     1.0, 1.0,
                     0.0, 1.0,
                    ];
    gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(textureCoords),
        gl.STATIC_DRAW);
    cubeVertexTextureCoordBuffer.itemSize = 2;
    cubeVertexTextureCoordBuffer.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 xRot = 0;
var yRot = 0;
var zRot = 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, [0.0, 0.0, -5.0]);

    mat4.rotate(mvMatrix, mvMatrix, degToRad(xRot), [1, 0, 0]);
    mat4.rotate(mvMatrix, mvMatrix, degToRad(yRot), [0, 1, 0]);
    mat4.rotate(mvMatrix, mvMatrix, degToRad(zRot), [0, 0, 1]);

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

    gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexTextureCoordBuffer);
    gl.vertexAttribPointer(shaderProgram.textureCoordAttribute,
        cubeVertexTextureCoordBuffer.itemSize, gl.FLOAT, false, 0, 0);

    gl.activeTexture(gl.TEXTURE0);
    gl.bindTexture(gl.TEXTURE_2D, myTexture);
    gl.uniform1i(shaderProgram.samplerUniform, 0);

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

        xRot += (90 * elapsed) / 1000.0;
        yRot += (90 * elapsed) / 1000.0;
        zRot += (90 * elapsed) / 1000.0;
    }
    lastTime = timeNow;
}
</script>