# 加载场景,基本相机操作
```html
<div class="page-header"><h3>10、加载场景,基本相机操作</h3></div>

<canvas id = "test10-canvas" width = "800" height = "600"></canvas>
<div id="loadingtext">正在加载世界……</div>
<br/>
(WSAD控制移动,逗号/句号 控制 上下看)

<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 = $("#test10-canvas")[0];
initGL(canvas);
initShaders();
initBuffers();
initTexture();

loadWorld();

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

$(document).keydown(handleKeyDown);
$(document).keyup(handleKeyUp);
}
function tick()
{
requestAnimFrame(tick);
handleKeys();
drawScene();
animate();
}
function loadWorld()
{
$.getJSON(
"/Public/json/world.json",
function(data)
{
handleLoadedWorld(data);
}
);
}
var worldVertexPositionBuffer = null;
var worldVertexTextureCoordBuffer = null;
function handleLoadedWorld(data)
{
var vertexCount = 0;
var vertexPositions = [];
var vertexTextureCoords = [];

for(var i = 0; typeof(data[i]) != "undefined"; i ++)
{
//环境中一个部分的顶点坐标
vertexPositions =
vertexPositions.concat(data[i].vertexPositions);
//然后是纹理坐标
vertexTextureCoords =
vertexTextureCoords.concat(data[i].vertexTextureCoords);
vertexCount ++;
}
worldVertexPositionBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, worldVertexPositionBuffer);
gl.bufferData(gl.ARRAY_BUFFER,
new Float32Array(vertexPositions), gl.STATIC_DRAW);
worldVertexPositionBuffer.itemSize = 3;
worldVertexPositionBuffer.numItems = data.vertexCount;

worldVertexTextureCoordBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, worldVertexTextureCoordBuffer);
gl.bufferData(gl.ARRAY_BUFFER,
new Float32Array(vertexTextureCoords), gl.STATIC_DRAW);
worldVertexTextureCoordBuffer.itemSize = 2;
worldVertexTextureCoordBuffer.numItems = data.vertexCount;

$("#loadingtext").text("");
}
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 crackTexture;
function initTexture()
{
crackTexture = gl.createTexture();
crackTexture.image = new Image();
crackTexture.image.onload = function()
{
handleLoadedTexture(crackTexture);
tick();
}
crackTexture.image.src = "/Public/image/cracktexture.jpg";
}
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.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 starVertexPositionBuffer;
var starVertexTextureCoordBuffer;

function initBuffers()
{
starVertexPositionBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, starVertexPositionBuffer);
vertices = [
-1.0, -1.0, 0.0,
1.0, -1.0, 0.0,
-1.0, 1.0, 0.0,
1.0, 1.0, 0.0
];
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices),
gl.STATIC_DRAW);
starVertexPositionBuffer.itemSize = 3;
starVertexPositionBuffer.numItems = 4;

starVertexTextureCoordBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, starVertexTextureCoordBuffer);
var textureCoords = [
0.0, 0.0,
1.0, 0.0,
0.0, 1.0,
1.0, 1.0
];
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(textureCoords),
gl.STATIC_DRAW);
starVertexTextureCoordBuffer.itemSize = 2;
starVertexTextureCoordBuffer.numItems = 4;
}


var currentlyPressedKeys = {};
function handleKeyDown(event)
{
currentlyPressedKeys[event.keyCode] = true;
}
function handleKeyUp(event)
{
currentlyPressedKeys[event.keyCode] = false;
}

var pitch = 0;
var pitchRate = 0;

var yaw = 0;
var yawRate = 0;
var xPos = 0;
var yPos = 0.4;
var zPos = 0;

var speed = 0;
function handleKeys()
{
if(currentlyPressedKeys[188])
{
//","/"<"逗号键
pitchRate = -0.1;
}
else if(currentlyPressedKeys[190])
{
//"."/">"句号键
pitchRate = 0.1;
}
else
{
pitchRate = 0;
}
if (currentlyPressedKeys[65])
{
//A
yawRate = 0.1;
}
else if (currentlyPressedKeys[68])
{
//D
yawRate = -0.1;
}
else
{
yawRate = 0;
}
if(currentlyPressedKeys[87])
{
//W
speed = 0.003;
}
else if(currentlyPressedKeys[83])
{
//S
speed = -0.003;
}
else
{
speed = 0;
}
}
function drawScene()
{
gl.viewport(0, 0, gl.viewportWidth, gl.viewportHeight);
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

if(worldVertexTextureCoordBuffer == null || worldVertexPositionBuffer == null)
{
return;
}
mat4.perspective(pMatrix, 45,
gl.viewportWidth / gl.viewportHeight, 0.1, 100.0);

mat4.identity(mvMatrix);

mat4.rotate(mvMatrix, mvMatrix, degToRad(-pitch), [1, 0, 0]);
mat4.rotate(mvMatrix, mvMatrix, degToRad(-yaw), [0, 1, 0]);
mat4.translate(mvMatrix, mvMatrix, [-xPos, -yPos, -zPos]);

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

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

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

setMatrixUniforms();
gl.drawArrays(gl.TRIANGLES, 0, worldVertexPositionBuffer.numItems);
}

function degToRad(degrees)
{
return degrees * Math.PI / 180;
}
var lastTime = 0;
var joggingAngle = 0;
function animate()
{
var timeNow = new Date().getTime();
if(lastTime != 0)
{
var elapsed = timeNow - lastTime;
if(speed != 0)
{
xPos -= Math.sin(degToRad(yaw)) * speed * elapsed;
zPos -= Math.cos(degToRad(yaw)) * speed * elapsed;
joggingAngle += elapsed * 0.6;
yPos = Math.sin(degToRad(joggingAngle)) / 20 + 0.4;
}
yaw += yawRate * elapsed;
pitch += pitchRate * elapsed;
}
lastTime = timeNow;
}
</script>
```