# 逐片元光照,多着色方案切换

```html
<div class="page-header"><h3>13、逐片元光照,多着色方案切换</h3></div>

<canvas id = "test13-canvas" width = "800" height = "600"></canvas>
<br/>

<input type="checkbox" id="lighting" checked /> 使用光照
<br/>
<input type="checkbox" id="per-fragment" checked /> 逐片元计算光照
<br/>
<input type="checkbox" id="textures" checked /> 使用纹理
<br/>
<h4>点光:</h4>
<table>
<tr>
<td><b>位置:</b></td>
<td>X: <input type="text" id="lightPositionX" value="0.0" /></td>
<td>Y: <input type="text" id="lightPositionY" value="0.0" /></td>
<td>Z: <input type="text" id="lightPositionZ" value="-5.0" /></td>
</tr>
<tr>
<td><b>颜色:</b></td>
<td>R: <input type="text" id="pointR" value="0.8" /></td>
<td>G: <input type="text" id="pointG" value="0.8" /></td>
<td>B: <input type="text" id="pointB" 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 = "per-vertex-lighting-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 uPointLightingLocation;
uniform vec3 uPointLightingColor;

uniform bool uUseLighting;

varying vec2 vTextureCoord;
varying vec3 vLightWeighting;

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

if (!uUseLighting)
{
vLightWeighting = vec3(1.0, 1.0, 1.0);
}
else
{
vec3 lightDirection =
normalize(uPointLightingLocation - mvPosition.xyz);

vec3 transformedNormal = uNMatrix * aVertexNormal;
float directionalLightWeighting =
max(dot(transformedNormal, lightDirection), 0.0);
vLightWeighting =
uAmbientColor + uPointLightingColor * directionalLightWeighting;
}
}
</script>

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

varying vec2 vTextureCoord;
varying vec3 vLightWeighting;

uniform bool uUseTextures;

uniform sampler2D uSampler;

void main(void)
{
vec4 fragmentColor;
if (uUseTextures)
{
fragmentColor = texture2D(uSampler, vec2(vTextureCoord.s, vTextureCoord.t));
}
else
{
fragmentColor = vec4(1.0, 1.0, 1.0, 1.0);
}
gl_FragColor = vec4(fragmentColor.rgb * vLightWeighting, fragmentColor.a);
}
</script>




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

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

varying vec2 vTextureCoord;
varying vec3 vTransformedNormal;
varying vec4 vPosition;


void main(void)
{
vPosition = uMVMatrix * vec4(aVertexPosition, 1.0);
gl_Position = uPMatrix * vPosition;
vTextureCoord = aTextureCoord;
vTransformedNormal = uNMatrix * aVertexNormal;
}
</script>
<script id = "per-fragment-lighting-fs" type = "x-shader/x-fragment">
precision mediump float;

varying vec2 vTextureCoord;
varying vec3 vTransformedNormal;
varying vec4 vPosition;

uniform bool uUseLighting;
uniform bool uUseTextures;

uniform vec3 uAmbientColor;

uniform vec3 uPointLightingLocation;
uniform vec3 uPointLightingColor;

uniform sampler2D uSampler;


void main(void)
{
vec3 lightWeighting;
if (!uUseLighting)
{
lightWeighting = vec3(1.0, 1.0, 1.0);
}
else
{
vec3 lightDirection =
normalize(uPointLightingLocation - vPosition.xyz);

float directionalLightWeighting =
max(dot(normalize(vTransformedNormal), lightDirection), 0.0);
lightWeighting =
uAmbientColor + uPointLightingColor * directionalLightWeighting;
}

vec4 fragmentColor;
if (uUseTextures)
{
fragmentColor =
texture2D(uSampler, vec2(vTextureCoord.s, vTextureCoord.t));
}
else
{
fragmentColor = vec4(1.0, 1.0, 1.0, 1.0);
}
gl_FragColor = vec4(fragmentColor.rgb * lightWeighting, fragmentColor.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 = $("#test13-canvas");
initGL(canvas[0]);
initShaders();
initBuffers();
initTexture();

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

waitTexture = setInterval("tick()", 100);
}

var textureFlag = [0, 0];
var startTick = false;
var waitTick;
function tick()
{
if(textureFlag[0] == 1 && textureFlag[1] == 1)
{
startTick = true;
textureFlag[0] = 2;
textureFlag[1] = 2;
clearInterval(waitTexture);
}
if(startTick)
{
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”。");
}
}

var moonTexture;
var crateTexture;
function initTexture()
{
moonTexture = gl.createTexture();
moonTexture.image = new Image();
moonTexture.image.onload = function()
{
handleLoadedTexture(moonTexture);
textureFlag[0] = true;
}
moonTexture.image.src = "/Public/image/moon.gif";


crateTexture = gl.createTexture();
crateTexture.image = new Image();
crateTexture.image.onload = function()
{
handleLoadedTexture(crateTexture);
textureFlag[1] = true;
}
crateTexture.image.src = "/Public/image/crate.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;
}
function createProgram(vertexShaderID, fragmentShaderID)
{
var vertexShader = getShader(gl, vertexShaderID);
var fragmentShader = getShader(gl, fragmentShaderID);

var program = gl.createProgram();
gl.attachShader(program, vertexShader);
gl.attachShader(program, fragmentShader);
gl.linkProgram(program);
if(!gl.getProgramParameter(program, gl.LINK_STATUS))
{
alert("无法初始化“Shader”。");
}

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

program.vertexNormalAttribute =
gl.getAttribLocation(program, "aVertexNormal");
gl.enableVertexAttribArray(program.vertexNormalAttribute);

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

program.pMatrixUniform =
gl.getUniformLocation(program, "uPMatrix");
program.mvMatrixUniform =
gl.getUniformLocation(program, "uMVMatrix");
program.nMatrixUniform =
gl.getUniformLocation(program, "uNMatrix");
program.samplerUniform =
gl.getUniformLocation(program, "uSampler");
program.useTexturesUniform =
gl.getUniformLocation(program, "uUseTextures");
program.useLightingUniform =
gl.getUniformLocation(program, "uUseLighting");
program.ambientColorUniform =
gl.getUniformLocation(program, "uAmbientColor");
program.pointLightingLocationUniform =
gl.getUniformLocation(program, "uPointLightingLocation");
program.pointLightingColorUniform =
gl.getUniformLocation(program, "uPointLightingColor");
return program;
}
var currentProgram;
var perVertexProgram;
var perFragmentProgram;
function initShaders()
{
perVertexProgram =
createProgram("per-vertex-lighting-vs", "per-vertex-lighting-fs");
perFragmentProgram =
createProgram("per-fragment-lighting-vs", "per-fragment-lighting-fs");
}

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(currentProgram.pMatrixUniform, false, pMatrix);
gl.uniformMatrix4fv(currentProgram.mvMatrixUniform, false, mvMatrix);

var normalMatrix = mat3.create();

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

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

var cubeVertexPositionBUffer;
var cubeVertexTextureCoordBuffer;
var cubeVertexIndexBuffer;
var cubeVertexNormalBuffer;

var moonVertexPositionBuffer;
var moonVertexNormalBuffer;
var moonVertexTextureCoordBuffer;
var moonVertexIndexBuffer;

function initBuffers()
{
//箱子
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;

cubeVertexNormalBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexNormalBuffer);
var vertexNormals = [
// 正面
0.0, 0.0, 1.0,
0.0, 0.0, 1.0,
0.0, 0.0, 1.0,
0.0, 0.0, 1.0,

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

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

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

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

// 左侧面
-1.0, 0.0, 0.0,
-1.0, 0.0, 0.0,
-1.0, 0.0, 0.0,
-1.0, 0.0, 0.0,
];
gl.bufferData(gl.ARRAY_BUFFER,
new Float32Array(vertexNormals), gl.STATIC_DRAW);
cubeVertexNormalBuffer.itemSize = 3;
cubeVertexNormalBuffer.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;

//月亮
var latitudeBands = 30;
var longitudeBands = 30;
var radius = 1;
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;
}

var moonAngle = 180;
var cubeAngle = 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);

var perFragmentLighting = $("#per-fragment").is(":checked");
if(perFragmentLighting)
{
currentProgram = perFragmentProgram;
}
else
{
currentProgram = perVertexProgram;
}
gl.useProgram(currentProgram);

var lighting = $("#lighting").is(":checked");
gl.uniform1i(currentProgram.useLightingUniform, lighting);
if(lighting)
{
gl.uniform3f(
currentProgram.ambientColorUniform,
parseFloat($("#ambientR").val()),
parseFloat($("#ambientG").val()),
parseFloat($("#ambientB").val())
);
gl.uniform3f(
currentProgram.pointLightingLocationUniform,
parseFloat($("#lightPositionX").val()),
parseFloat($("#lightPositionY").val()),
parseFloat($("#lightPositionZ").val())
);

gl.uniform3f(
currentProgram.pointLightingColorUniform,
parseFloat($("#pointR").val()),
parseFloat($("#pointG").val()),
parseFloat($("#pointB").val())
);

}

var textures = $("#textures").is(":checked");
gl.uniform1i(currentProgram.useTexturesUniform, textures);

mat4.identity(mvMatrix);
mat4.translate(mvMatrix, mvMatrix, [0, 0, -5]);
mat4.rotate(mvMatrix, mvMatrix, degToRad(30), [1, 0, 0]);

mvPushMatrix();

mat4.rotate(mvMatrix, mvMatrix, degToRad(moonAngle), [0, 1, 0]);
mat4.translate(mvMatrix, mvMatrix, [2, 0, 0]);

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

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

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

gl.bindBuffer(gl.ARRAY_BUFFER, moonVertexNormalBuffer);
gl.vertexAttribPointer(currentProgram.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);

mvPopMatrix();

mvPushMatrix();
mat4.rotate(mvMatrix, mvMatrix, degToRad(cubeAngle), [0, 1, 0]);
mat4.translate(mvMatrix, mvMatrix, [1.25, 0, 0]);

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

gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexNormalBuffer);
gl.vertexAttribPointer(currentProgram.vertexNormalAttribute,
cubeVertexNormalBuffer.itemSize, gl.FLOAT, false, 0, 0);

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

gl.activeTexture(gl.TEXTURE0);
gl.bindTexture(gl.TEXTURE_2D, crateTexture);
gl.uniform1i(currentProgram.samplerUniform, 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;

moonAngle += 0.05 * elapsed;
cubeAngle += 0.05 * elapsed;
}
lastTime = timeNow;
}
</script>
```