键盘交互与纹理过滤

<div class="page-header"><h3>6、键盘输入与纹理过滤</h3></div>

<canvas id = "test06-canvas" width = "800" height = "600"></canvas>
<li>逗号/句号 控制 靠近/远离</li>
<li>WSAD键控制四个方向旋转速度</li>
<li>F键控制纹理过滤类型切换</li>
<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 = $("#test06-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);

    $(document).keydown(handleKeyDown);
    $(document).keyup(handleKeyUp);
}
var crateTextures = Array();
function initTexture()
{
    var crateImage = new Image();
    for(var i = 0; i < 3; i ++)
    {
        var texture = gl.createTexture();
        texture.image = crateImage;
        crateTextures.push(texture);
    }
    crateImage.onload = function()
    {
        handleLoadedTexture(crateTextures);
        tick();
    }
    crateImage.src = "/Public/image/crate.gif";
}
function handleLoadedTexture(textures)
{
    gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL, 1);

    gl.bindTexture(gl.TEXTURE_2D, textures[0]);
    gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, 
        gl.UNSIGNED_BYTE, textures[0].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, textures[1]);
    gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, 
        gl.UNSIGNED_BYTE, textures[1].image);
    gl.texParameteri(gl.TEXTURE_2D, 
        gl.TEXTURE_MAG_FILTER, gl.LINEAR);
    gl.texParameteri(gl.TEXTURE_2D, 
        gl.TEXTURE_MIN_FILTER, gl.LINEAR);

    gl.bindTexture(gl.TEXTURE_2D, textures[2]);
    gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, 
        gl.UNSIGNED_BYTE, textures[2].image);
    gl.texParameteri(gl.TEXTURE_2D, 
        gl.TEXTURE_MAG_FILTER, gl.LINEAR);
    gl.texParameteri(gl.TEXTURE_2D, 
        gl.TEXTURE_MIN_FILTER, gl.LINEAR_MIPMAP_NEAREST);

    gl.generateMipmap(gl.TEXTURE_2D);

    gl.bindTexture(gl.TEXTURE_2D, null);
}
function tick()
{
    requestAnimFrame(tick);
    handleKeys();
    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 xSpeed = 0;

var yRot = 0;
var ySpeed = 0;

var z = -5.0;

var filter = 0;

var currentlyPressedKeys = {};
function handleKeyDown(event)
{
    currentlyPressedKeys[event.keyCode] = true;
    if(String.fromCharCode(event.keyCode) == "F")
    {
        filter += 1;
        if(filter == 3)
        {
            filter = 0;
        }
    }
}
function handleKeyUp(event)
{
    currentlyPressedKeys[event.keyCode] = false;
}
function handleKeys()
{
    if(currentlyPressedKeys[190])
    {
        //"."/">"句号键
        z -= 0.05;
    }
    if(currentlyPressedKeys[188])
    {
        //","/"<"逗号键
        z += 0.05;
    }
    if(currentlyPressedKeys[65])
    {
        //A
        ySpeed -= 1;
    }
    if(currentlyPressedKeys[68])
    {
        //D
        ySpeed += 1;
    }
    if(currentlyPressedKeys[87])
    {
        //W
        xSpeed -= 1;
    }
    if(currentlyPressedKeys[83])
    {
        //S
        xSpeed += 1;
    }    
}
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, z]);

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

    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, crateTextures[filter]);
    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 += (xSpeed * elapsed) / 1000.0;
        yRot += (ySpeed * elapsed) / 1000.0;
    }
    lastTime = timeNow;
}
</script>