# 引入纹理

```html
<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>
```