球、旋转矩阵、鼠标事件

<div class="page-header"><h3>11、球、旋转矩阵、鼠标事件</h3></div>

<canvas id = "test11-canvas" width = "800" height = "600"></canvas>

<br/>
<input type="checkbox" id="lighting" checked /> 使用光照
<br/>
(鼠标拖拽对月球进行转动)
<br/>
<h4>方向光:</h4>
<table>
    <tr>
        <td><b>方向:</b></td>
        <td>X: <input type="text" id="lightDirectionX" value="-0.25" /></td>
        <td>Y: <input type="text" id="lightDirectionY" value="-0.25" /></td>
        <td>Z: <input type="text" id="lightDirectionZ" value="-1.0" /></td>
    </tr>
    <tr>
        <td><b>颜色:</b></td>
        <td>R: <input type="text" id="directionalR" value="0.8" /></td>
        <td>G: <input type="text" id="directionalG" value="0.8" /></td>
        <td>B: <input type="text" id="directionalB" value="0.8" /></td>
    </tr>
</table>
<h4>环境光:</h4>
<table style="border: 0; padding: 10px;">
    <tr>
        <td><b>颜色:</b></td>
        <td>R: <input type="text" id="ambientR" value="0.2" /></td>
        <td>G: <input type="text" id="ambientG" value="0.2" /></td>
        <td>B: <input type="text" id="ambientB" value="0.2" /></td>
    </tr>
</table>
<br/>
月球表面纹理图片来自：
<a href="http://maps.jpl.nasa.gov/">the Jet Propulsion Laboratory</a>.
<script id = "shader-vs" type = "x-shader/x-vertex">
    attribute vec3 aVertexPosition;
    attribute vec3 aVertexNormal;
    attribute vec2 aTextureCoord;

    uniform mat4 uMVMatrix;
    uniform mat4 uPMatrix;
    uniform mat3 uNMatrix;

    uniform vec3 uAmbientColor;

    uniform vec3 uLightingDirection;
    uniform vec3 uDirectionalColor;

    uniform bool uUseLighting;

    varying vec2 vTextureCoord;
    varying vec3 vLightWeighting;

    void main(void)
    {
        gl_Position = uPMatrix * uMVMatrix * vec4(aVertexPosition, 1.0);
        vTextureCoord = aTextureCoord;

        if(!uUseLighting)
        {
            vLightWeighting = vec3(1.0, 1.0, 1.0);
        }
        else
        {
            vec3 transformedNormal = uNMatrix * aVertexNormal;
            float directionalLightWeighting = 
                max(dot(transformedNormal, uLightingDirection), 0.0);
            vLightWeighting = 
                uAmbientColor + uDirectionalColor * directionalLightWeighting;
        }
    }
</script>

<script id = "shader-fs" type = "x-shader/x-fragment">
    precision mediump float;
    varying vec2 vTextureCoord;
    varying vec3 vLightWeighting;

    uniform sampler2D uSampler;
    void main(void)
    {
        vec4 textureColor = 
            texture2D(uSampler, vec2(vTextureCoord.s, vTextureCoord.t));
        gl_FragColor = 
            vec4(textureColor.rgb * vLightWeighting, textureColor.a);
    }
</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 = $("#test11-canvas");
    initGL(canvas[0]);
    initShaders();
    initBuffers();
    initTexture();

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

    canvas.mousedown(handleMouseDown);
    $(document).mouseup(handleMouseUp);
    $(document).mousemove(handleMouseMove);
}
function tick()
{
    requestAnimFrame(tick);
    drawScene();
}
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”。");
    }
}

var moonTexture;
function initTexture()
{
    moonTexture = gl.createTexture();
    moonTexture.image = new Image();
    moonTexture.image.onload = function()
    {
        handleLoadedTexture(moonTexture);
        tick();
    }
    moonTexture.image.src = "/Public/image/moon.gif";
}
function handleLoadedTexture(texture)
{
    gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL, 1);


    gl.bindTexture(gl.TEXTURE_2D, texture);
    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.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 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.vertexNormalAttribute = 
        gl.getAttribLocation(shaderProgram, "aVertexNormal");
    gl.enableVertexAttribArray(shaderProgram.vertexNormalAttribute);

    shaderProgram.textureCoordAttribute = 
        gl.getAttribLocation(shaderProgram, "aTextureCoord");
    gl.enableVertexAttribArray(shaderProgram.textureCoordAttribute);

    shaderProgram.pMatrixUniform = 
        gl.getUniformLocation(shaderProgram, "uPMatrix");
    shaderProgram.mvMatrixUniform = 
        gl.getUniformLocation(shaderProgram, "uMVMatrix");
    shaderProgram.nMatrixUniform  = 
        gl.getUniformLocation(shaderProgram, "uNMatrix");
    shaderProgram.samplerUniform = 
        gl.getUniformLocation(shaderProgram, "uSampler");
    shaderProgram.useLightingUniform = 
        gl.getUniformLocation(shaderProgram, "uUseLighting");
    shaderProgram.ambientColorUniform = 
        gl.getUniformLocation(shaderProgram, "uAmbientColor");
    shaderProgram.lightingDirectionUniform = 
        gl.getUniformLocation(shaderProgram, "uLightingDirection");
    shaderProgram.directionalColorUniform = 
        gl.getUniformLocation(shaderProgram, "uDirectionalColor");
}


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 normalMatrix = mat3.create();

    mat3.fromMat4(normalMatrix, mvMatrix);
    mat3.invert(normalMatrix, normalMatrix);
    mat3.transpose(normalMatrix, normalMatrix);

    gl.uniformMatrix3fv(shaderProgram.nMatrixUniform, false, normalMatrix);
}

var mouseDown = false;
var lastMouseX = null;
var lastMouseY = null;
var moonRotationMatrix = mat4.create();
mat4.identity(moonRotationMatrix);
function handleMouseDown(event)
{
    mouseDown = true;
    lastMouseX = event.clientX;
    lastMouseY = event.clientY;
}
function handleMouseUp(event)
{
    mouseDown = false;
}
function handleMouseMove(event)
{
    if(!mouseDown)
    {
        return;
    }
    var newX = event.clientX;
    var newY = event.clientY;
    var newRotationMatrix = mat4.create();
    mat4.identity(newRotationMatrix);

    var deltaX = newX - lastMouseX;
    mat4.rotate(newRotationMatrix, newRotationMatrix, 
        degToRad(deltaX / 10), [0, 1, 0]);
    var deltaY = newY - lastMouseY;
    mat4.rotate(newRotationMatrix, newRotationMatrix, 
        degToRad(deltaY / 10), [1, 0, 0]);

    mat4.multiply(moonRotationMatrix, newRotationMatrix, moonRotationMatrix);

    lastMouseX = newX;
    lastMouseY = newY;
}
function equal(a, b)
{
    for(var i = 0; i < a.length; i ++)
        if(a[i] != b[i]) return false;
    return true;
}
var moonVertexPositionBuffer;
var moonVertexNormalBuffer;
var moonVertexTextureCoordBuffer;
var moonVertexIndexBuffer;

function initBuffers()
{
    var latitudeBands = 30;
    var longitudeBands = 30;
    var radius = 2;
    var vertexPositionData = [];
    var normalData = [];
    var textureCoordData = [];
    for(var latNumber = 0; latNumber <= latitudeBands; latNumber ++)
    {
        var theta = latNumber * Math.PI / latitudeBands;
        var sinTheta = Math.sin(theta);
        var cosTheta = Math.cos(theta);
        for(var longNumber = 0; longNumber <= longitudeBands; longNumber ++)
        {
            var phi = longNumber * 2 * Math.PI / longitudeBands;
            var sinPhi = Math.sin(phi);
            var cosPhi = Math.cos(phi);
            var x = cosPhi * sinTheta;
            var y = cosTheta;
            var z = sinPhi * sinTheta;
            var u = 1 - (longNumber / longitudeBands);
            var v = 1 - (latNumber / latitudeBands);

            normalData.push(x);
            normalData.push(y);
            normalData.push(z);
            textureCoordData.push(u);
            textureCoordData.push(v);
            vertexPositionData.push(radius * x);
            vertexPositionData.push(radius * y);
            vertexPositionData.push(radius * z);
        }
    }
    var indexData = [];
    for(var latNumber = 0; latNumber < latitudeBands; latNumber ++)
    {
        for(var longNumber = 0; longNumber < longitudeBands; longNumber ++)
        {
            var first = (latNumber * (longitudeBands + 1)) + longNumber;
            var second = first + longitudeBands + 1;
            indexData.push(first);
            indexData.push(second);
            indexData.push(first + 1);
            indexData.push(second);
            indexData.push(second + 1);
            indexData.push(first + 1);
        }
    }
    moonVertexNormalBuffer = gl.createBuffer();
    gl.bindBuffer(gl.ARRAY_BUFFER, moonVertexNormalBuffer);
    gl.bufferData(gl.ARRAY_BUFFER, 
        new Float32Array(normalData), gl.STATIC_DRAW);
    moonVertexNormalBuffer.itemSize = 3;
    moonVertexNormalBuffer.numItems = normalData.length / 3;

    moonVertexTextureCoordBuffer = gl.createBuffer();
    gl.bindBuffer(gl.ARRAY_BUFFER, moonVertexTextureCoordBuffer);
    gl.bufferData(gl.ARRAY_BUFFER, 
        new Float32Array(textureCoordData), gl.STATIC_DRAW);
    moonVertexTextureCoordBuffer.itemSize = 2;
    moonVertexTextureCoordBuffer.numItems = textureCoordData.length / 2;

    moonVertexPositionBuffer = gl.createBuffer();
    gl.bindBuffer(gl.ARRAY_BUFFER, moonVertexPositionBuffer);
    gl.bufferData(gl.ARRAY_BUFFER, 
        new Float32Array(vertexPositionData), gl.STATIC_DRAW);
    moonVertexPositionBuffer.itemSize = 3;
    moonVertexPositionBuffer.numItems = vertexPositionData.length / 3;

    moonVertexIndexBuffer = gl.createBuffer();
    gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, moonVertexIndexBuffer);
    gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, 
        new Uint16Array(indexData), gl.STATIC_DRAW);
    moonVertexIndexBuffer.itemSize = 1;
    moonVertexIndexBuffer.numItems = indexData.length;
}
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);

    var lighting = $("#lighting").is(":checked");
    gl.uniform1i(shaderProgram.useLightingUniform, lighting);
    if(lighting)
    {
        gl.uniform3f(
            shaderProgram.ambientColorUniform,
            parseFloat($("#ambientR").val()),
            parseFloat($("#ambientG").val()),
            parseFloat($("#ambientB").val())
            );
        var lightingDirection = [
            parseFloat($("#lightDirectionX").val()),
            parseFloat($("#lightDirectionY").val()),
            parseFloat($("#lightDirectionZ").val())
            ];
        var adjustedLD = vec3.create();
        vec3.normalize(adjustedLD, lightingDirection);
        vec3.scale(adjustedLD, adjustedLD, -1);
        gl.uniform3fv(shaderProgram.lightingDirectionUniform, adjustedLD);
        gl.uniform3f(
            shaderProgram.directionalColorUniform,
            parseFloat($("#directionalR").val()),
            parseFloat($("#directionalG").val()),
            parseFloat($("#directionalB").val())
            );
    }

    mat4.identity(mvMatrix);
    mat4.translate(mvMatrix, mvMatrix, [0, 0, -6]);

    mat4.multiply(mvMatrix, mvMatrix, moonRotationMatrix);

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

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

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

    gl.bindBuffer(gl.ARRAY_BUFFER, moonVertexNormalBuffer);
    gl.vertexAttribPointer(shaderProgram.vertexNormalAttribute, 
        moonVertexNormalBuffer.itemSize, gl.FLOAT, false, 0, 0);

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

function degToRad(degrees)
{
    return degrees * Math.PI / 180;
}
</script>