WebGL自学教程——WebGL示例：7.1 改进的立方体程序(上)
7.1 改进的立方体程序(上)
如上一章所提，直接以顶点的方式提供数据，让后用WebGL函数drawArrays绘图，会导致很大的内容占用和带宽。比如，立方体只有8个顶点，但为了使用drawArrays绘画它，我们足足提供了36个顶点的数据。一种改善的做法是，仅将立方体的8个顶点保存在缓冲中，在绘图时，我们通过指定各个顶点在该缓冲中的索引进行。以立方体为例，我们首先定义它的8个顶点：
那么，立方体的六个面就可以通过下面的这些三角形来表示：
前：123、341
后：587、765
左：437、784
右：562、215
上：514、485
下：267、732
那么，我们在绘画这个立方体时，只需要传递这36个索引，每个索引用BYTE就可以表示。
通过索引绘图的WebGL函数为drawElements(mode, count, type, offset)。第一个参数mode和drawArray相同，都用来指明绘画类型，比如线、三角形、三角带等。count指明要绘画索引的个数。type指明保存索引的数据类型，可以是UNSIGNED_BYTE、UNSIGNED_SHORT。offset指明起始元素索引的偏移，以字节为单位。当type为UNSIGNED_SHORT时，该值必须是2的整数倍。该值指明我们要从哪个索引开始画起。比如，我们把三角形的索引和立方体的索引保存在了同一个索引缓冲中，并以BYTE类型保存索引数据，用三个索引表示一个顶点。三角形索引在前，立方体索引在后，那么，我们在绘画立方体时，就要跳过前面的三角形索引。相应地，offset的值如下计算：1字节/数据*3个数据/顶点*3个顶点=9个字节。
下面是完整的源码：
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=gb2312">
<script type="text/javascript" src="glMatrix-0.9.5.js"></script>
<script id="shader-vs" type="x-shader/x-vertex">
attribute vec3 v3Position;
attribute vec2 v2CubeTexST;
uniform mat4 um4Rotate;
varying vec2 v_texCoord;
void main(void)
{
v_texCoord = vec2((v2CubeTexST.x+1.0)/2.0, 1.0-(v2CubeTexST.y+1.0)/2.0);
gl_Position = um4Rotate * vec4(v3Position, 1.0);
}
</script>
<script id="shader-fs" type="x-shader/x-fragment">
#ifdef GL_FRAGMENT_PRECISION_HIGH
precision highp float;
#else
precision mediump float;
#endif
uniform sampler2D s_texture;
varying vec2 v_texCoord;
void main(void)
{
gl_FragColor = texture2D(s_texture, v_texCoord);
}
</script>
<script>
function ShaderSourceFromScript(scriptID)
{
var shaderScript = document.getElementById(scriptID);
if (shaderScript == null) return "";
var sourceCode = "";
var child = shaderScript.firstChild;
while (child)
{
if (child.nodeType == child.TEXT_NODE ) sourceCode += child.textContent;
child = child.nextSibling;
}
return sourceCode;
}
var webgl = null;
var vertexShaderObject = null;
var fragmentShaderObject = null;
var programObject = null;
var cubeBuffer = null;
var cubeIndexBuffer = null;
var v3PositionIndex = 0;
var textureObject = null;
var samplerIndex = -1;
var interval = 300;
var angle = 0;
var um4RotateIndex = -1;
var leftKeyDown = false;
var rightKeyDown = false;
var cubeTexSTBuffer = null;
var cubeTexSTIndex = 1;
var angleX = 0;
var upKeyDown = false;
var downKeyDown = false;
function LoadData()
{
var jsCubeData = [
0.5, 0.5, 0.5,
0.5, -0.5, 0.5,
-0.5, -0.5, 0.5,
-0.5, 0.5, 0.5,
0.5, 0.5, -0.5,
0.5, -0.5, -0.5,
-0.5, -0.5, -0.5,
-0.5, 0.5, -0.5
];
cubeBuffer = webgl.createBuffer();
webgl.bindBuffer(webgl.ARRAY_BUFFER, cubeBuffer);
webgl.bufferData(webgl.ARRAY_BUFFER, new Float32Array(jsCubeData), webgl.STATIC_DRAW);
var jsCubeIndex = [
//前
1,2,3,
3,4,1,
//后
5,8,7,
7,6,5,
//左
4,3,7,
7,8,4,
//右
5,6,2,
2,1,5,
//上
5,1,4,
4,8,5,
//下
2,6,7,
7,3,2
];
//数组中的是1-8的编号，要处理为0-7的索引
for(var i=0; i<jsCubeIndex.length; ++i) --jsCubeIndex[i];
cubeIndexBuffer = webgl.createBuffer();
webgl.bindBuffer(webgl.ELEMENT_ARRAY_BUFFER, cubeIndexBuffer);
webgl.bufferData(webgl.ELEMENT_ARRAY_BUFFER, new Uint8Array(jsCubeIndex), webgl.STATIC_DRAW);
var jsCubeTexST = [
//前
0.5, 0.5,
0.5, -0.5,
-0.5, -0.5,
-0.5, -0.5,
-0.5, 0.5,
0.5, 0.5,
//后
0.5, 0.5,
-0.5, 0.5,
-0.5, -0.5,
-0.5, -0.5,
0.5, -0.5,
0.5, 0.5,
//左
0.5, 0.5,
-0.5, 0.5,
-0.5, -0.5,
-0.5, -0.5,
0.5, -0.5,
0.5, 0.5,
//右
0.5, -0.5,
-0.5, -0.5,
-0.5, 0.5,
-0.5, 0.5,
0.5, 0.5,
0.5, -0.5,
//上
0.5, -0.5,
0.5, 0.5,
-0.5, 0.5,
-0.5, 0.5,
-0.5, -0.5,
0.5, -0.5,
//下
0.5, 0.5,
0.5, -0.5,
-0.5, -0.5,
-0.5, -0.5,
-0.5, 0.5,
0.5, 0.5
];
cubeTexSTBuffer = webgl.createBuffer();
webgl.bindBuffer(webgl.ARRAY_BUFFER, cubeTexSTBuffer);
webgl.bufferData(webgl.ARRAY_BUFFER, new Float32Array(jsCubeTexST), webgl.STATIC_DRAW);
textureObject = webgl.createTexture();
webgl.bindTexture(webgl.TEXTURE_2D, textureObject);
var img = document.getElementById('myTexture');
webgl.texImage2D(webgl.TEXTURE_2D, 0, webgl.RGB, webgl.RGB, webgl.UNSIGNED_BYTE, img);
return 0;
}
function RenderScene()
{
webgl.clearColor(0.0, 0.0, 0.0, 1.0);
webgl.clearDepth(1.0);
webgl.clear(webgl.COLOR_BUFFER_BIT|webgl.DEPTH_BUFFER_BIT);
webgl.bindBuffer(webgl.ARRAY_BUFFER, cubeTexSTBuffer);
webgl.enableVertexAttribArray(cubeTexSTIndex);
webgl.vertexAttribPointer(cubeTexSTIndex, 2, webgl.FLOAT, false, 0, 0);
webgl.texParameteri(webgl.TEXTURE_2D, webgl.TEXTURE_MIN_FILTER, webgl.NEAREST);
webgl.texParameteri(webgl.TEXTURE_2D, webgl.TEXTURE_MAG_FILTER, webgl.NEAREST);
webgl.texParameteri(webgl.TEXTURE_2D, webgl.TEXTURE_WRAP_S, webgl.CLAMP_TO_EDGE); //注意，部分数值不被支持，如REPEAT，因为我们的纹理的宽度和高度不是2的整数次方
webgl.texParameteri(webgl.TEXTURE_2D, webgl.TEXTURE_WRAP_T, webgl.CLAMP_TO_EDGE);
webgl.activeTexture(webgl.TEXTURE0);
webgl.bindTexture(webgl.TEXTURE_2D, textureObject);
webgl.uniform1i(samplerIndex, 0);
var m4Rotate = mat4.create();
mat4.identity(m4Rotate);
mat4.rotateZ(m4Rotate, angle*Math.PI/180);
mat4.rotateX(m4Rotate, angleX*Math.PI/180);
webgl.uniformMatrix4fv(um4RotateIndex, false, m4Rotate);
webgl.enable(webgl.DEPTH_TEST);
webgl.frontFace(webgl.CW);
webgl.bindBuffer(webgl.ARRAY_BUFFER, cubeBuffer);
webgl.bindBuffer(webgl.ELEMENT_ARRAY_BUFFER, cubeIndexBuffer);
webgl.enableVertexAttribArray(v3PositionIndex);
webgl.vertexAttribPointer(v3PositionIndex, 3, webgl.FLOAT, false, 0, 0);
webgl.drawElements(webgl.TRIANGLES, 36, webgl.UNSIGNED_BYTE, 0);
}
function RotateTriangle()
{
if(leftKeyDown) angle += 10;
if(rightKeyDown) angle -= 10;
if(angle >= 360) angle -= 360;
if(angle < 0) angle += 360;
if(upKeyDown) angleX += 10;
if(downKeyDown) angleX -= 10;
if(angleX >= 360) angleX -= 360;
if(angleX < 0) angleX += 360;
RenderScene();
}
document.onkeydown = function(e)
{
if(e.keyCode == 37) leftKeyDown = true;
if(e.keyCode == 39) rightKeyDown = true;
if(e.keyCode == 38) upKeyDown = true;
if(e.keyCode == 40) downKeyDown = true;
}
document.onkeyup = function(e)
{
if(e.keyCode == 37) leftKeyDown = false;
if(e.keyCode == 39) rightKeyDown = false;
if(e.keyCode == 38) upKeyDown = false;
if(e.keyCode == 40) downKeyDown = false;
}
function Init()
{
var myCanvasObject = document.getElementById('myCanvas');
webgl = myCanvasObject.getContext("experimental-webgl");
webgl.viewport(0, 0, myCanvasObject.clientWidth, myCanvasObject.clientHeight);
vertexShaderObject = webgl.createShader(webgl.VERTEX_SHADER);
fragmentShaderObject = webgl.createShader(webgl.FRAGMENT_SHADER);
webgl.shaderSource(vertexShaderObject, ShaderSourceFromScript("shader-vs"));
webgl.shaderSource(fragmentShaderObject, ShaderSourceFromScript("shader-fs"));
webgl.compileShader(vertexShaderObject);
webgl.compileShader(fragmentShaderObject);
if(!webgl.getShaderParameter(vertexShaderObject, webgl.COMPILE_STATUS)){alert(webgl.getShaderInfoLog(vertexShaderObject));return;}
if(!webgl.getShaderParameter(fragmentShaderObject, webgl.COMPILE_STATUS)){alert(webgl.getShaderInfoLog(fragmentShaderObject));return;}
programObject = webgl.createProgram();
webgl.attachShader(programObject, vertexShaderObject);
webgl.attachShader(programObject, fragmentShaderObject);
webgl.bindAttribLocation(programObject, v3PositionIndex, "v3Position");
webgl.bindAttribLocation(programObject, cubeTexSTIndex, "v2CubeTexST");
webgl.linkProgram(programObject);
if(!webgl.getProgramParameter(programObject, webgl.LINK_STATUS)){alert(webgl.getProgramInfoLog(programObject));return;}
samplerIndex = webgl.getUniformLocation(programObject, "s_texture");
um4RotateIndex = webgl.getUniformLocation(programObject, "um4Rotate");
webgl.useProgram(programObject);
if(LoadData() != 0){alert("error:LoadData()!");return;}
window.setInterval("RotateTriangle()", interval);
}
</script>
</head>
<body onload='Init()'>
<canvas id="myCanvas" style="border:1px solid red;" width='600px' height='450px'></canvas>
<img id="myTexture" src='texture.bmp'>
</body>
</html>
<head>
<meta http-equiv="content-type" content="text/html; charset=gb2312">
<script type="text/javascript" src="glMatrix-0.9.5.js"></script>
<script id="shader-vs" type="x-shader/x-vertex">
attribute vec3 v3Position;
attribute vec2 v2CubeTexST;
uniform mat4 um4Rotate;
varying vec2 v_texCoord;
void main(void)
{
v_texCoord = vec2((v2CubeTexST.x+1.0)/2.0, 1.0-(v2CubeTexST.y+1.0)/2.0);
gl_Position = um4Rotate * vec4(v3Position, 1.0);
}
</script>
<script id="shader-fs" type="x-shader/x-fragment">
#ifdef GL_FRAGMENT_PRECISION_HIGH
precision highp float;
#else
precision mediump float;
#endif
uniform sampler2D s_texture;
varying vec2 v_texCoord;
void main(void)
{
gl_FragColor = texture2D(s_texture, v_texCoord);
}
</script>
<script>
function ShaderSourceFromScript(scriptID)
{
var shaderScript = document.getElementById(scriptID);
if (shaderScript == null) return "";
var sourceCode = "";
var child = shaderScript.firstChild;
while (child)
{
if (child.nodeType == child.TEXT_NODE ) sourceCode += child.textContent;
child = child.nextSibling;
}
return sourceCode;
}
var webgl = null;
var vertexShaderObject = null;
var fragmentShaderObject = null;
var programObject = null;
var cubeBuffer = null;
var cubeIndexBuffer = null;
var v3PositionIndex = 0;
var textureObject = null;
var samplerIndex = -1;
var interval = 300;
var angle = 0;
var um4RotateIndex = -1;
var leftKeyDown = false;
var rightKeyDown = false;
var cubeTexSTBuffer = null;
var cubeTexSTIndex = 1;
var angleX = 0;
var upKeyDown = false;
var downKeyDown = false;
function LoadData()
{
var jsCubeData = [
0.5, 0.5, 0.5,
0.5, -0.5, 0.5,
-0.5, -0.5, 0.5,
-0.5, 0.5, 0.5,
0.5, 0.5, -0.5,
0.5, -0.5, -0.5,
-0.5, -0.5, -0.5,
-0.5, 0.5, -0.5
];
cubeBuffer = webgl.createBuffer();
webgl.bindBuffer(webgl.ARRAY_BUFFER, cubeBuffer);
webgl.bufferData(webgl.ARRAY_BUFFER, new Float32Array(jsCubeData), webgl.STATIC_DRAW);
var jsCubeIndex = [
//前
1,2,3,
3,4,1,
//后
5,8,7,
7,6,5,
//左
4,3,7,
7,8,4,
//右
5,6,2,
2,1,5,
//上
5,1,4,
4,8,5,
//下
2,6,7,
7,3,2
];
//数组中的是1-8的编号，要处理为0-7的索引
for(var i=0; i<jsCubeIndex.length; ++i) --jsCubeIndex[i];
cubeIndexBuffer = webgl.createBuffer();
webgl.bindBuffer(webgl.ELEMENT_ARRAY_BUFFER, cubeIndexBuffer);
webgl.bufferData(webgl.ELEMENT_ARRAY_BUFFER, new Uint8Array(jsCubeIndex), webgl.STATIC_DRAW);
var jsCubeTexST = [
//前
0.5, 0.5,
0.5, -0.5,
-0.5, -0.5,
-0.5, -0.5,
-0.5, 0.5,
0.5, 0.5,
//后
0.5, 0.5,
-0.5, 0.5,
-0.5, -0.5,
-0.5, -0.5,
0.5, -0.5,
0.5, 0.5,
//左
0.5, 0.5,
-0.5, 0.5,
-0.5, -0.5,
-0.5, -0.5,
0.5, -0.5,
0.5, 0.5,
//右
0.5, -0.5,
-0.5, -0.5,
-0.5, 0.5,
-0.5, 0.5,
0.5, 0.5,
0.5, -0.5,
//上
0.5, -0.5,
0.5, 0.5,
-0.5, 0.5,
-0.5, 0.5,
-0.5, -0.5,
0.5, -0.5,
//下
0.5, 0.5,
0.5, -0.5,
-0.5, -0.5,
-0.5, -0.5,
-0.5, 0.5,
0.5, 0.5
];
cubeTexSTBuffer = webgl.createBuffer();
webgl.bindBuffer(webgl.ARRAY_BUFFER, cubeTexSTBuffer);
webgl.bufferData(webgl.ARRAY_BUFFER, new Float32Array(jsCubeTexST), webgl.STATIC_DRAW);
textureObject = webgl.createTexture();
webgl.bindTexture(webgl.TEXTURE_2D, textureObject);
var img = document.getElementById('myTexture');
webgl.texImage2D(webgl.TEXTURE_2D, 0, webgl.RGB, webgl.RGB, webgl.UNSIGNED_BYTE, img);
return 0;
}
function RenderScene()
{
webgl.clearColor(0.0, 0.0, 0.0, 1.0);
webgl.clearDepth(1.0);
webgl.clear(webgl.COLOR_BUFFER_BIT|webgl.DEPTH_BUFFER_BIT);
webgl.bindBuffer(webgl.ARRAY_BUFFER, cubeTexSTBuffer);
webgl.enableVertexAttribArray(cubeTexSTIndex);
webgl.vertexAttribPointer(cubeTexSTIndex, 2, webgl.FLOAT, false, 0, 0);
webgl.texParameteri(webgl.TEXTURE_2D, webgl.TEXTURE_MIN_FILTER, webgl.NEAREST);
webgl.texParameteri(webgl.TEXTURE_2D, webgl.TEXTURE_MAG_FILTER, webgl.NEAREST);
webgl.texParameteri(webgl.TEXTURE_2D, webgl.TEXTURE_WRAP_S, webgl.CLAMP_TO_EDGE); //注意，部分数值不被支持，如REPEAT，因为我们的纹理的宽度和高度不是2的整数次方
webgl.texParameteri(webgl.TEXTURE_2D, webgl.TEXTURE_WRAP_T, webgl.CLAMP_TO_EDGE);
webgl.activeTexture(webgl.TEXTURE0);
webgl.bindTexture(webgl.TEXTURE_2D, textureObject);
webgl.uniform1i(samplerIndex, 0);
var m4Rotate = mat4.create();
mat4.identity(m4Rotate);
mat4.rotateZ(m4Rotate, angle*Math.PI/180);
mat4.rotateX(m4Rotate, angleX*Math.PI/180);
webgl.uniformMatrix4fv(um4RotateIndex, false, m4Rotate);
webgl.enable(webgl.DEPTH_TEST);
webgl.frontFace(webgl.CW);
webgl.bindBuffer(webgl.ARRAY_BUFFER, cubeBuffer);
webgl.bindBuffer(webgl.ELEMENT_ARRAY_BUFFER, cubeIndexBuffer);
webgl.enableVertexAttribArray(v3PositionIndex);
webgl.vertexAttribPointer(v3PositionIndex, 3, webgl.FLOAT, false, 0, 0);
webgl.drawElements(webgl.TRIANGLES, 36, webgl.UNSIGNED_BYTE, 0);
}
function RotateTriangle()
{
if(leftKeyDown) angle += 10;
if(rightKeyDown) angle -= 10;
if(angle >= 360) angle -= 360;
if(angle < 0) angle += 360;
if(upKeyDown) angleX += 10;
if(downKeyDown) angleX -= 10;
if(angleX >= 360) angleX -= 360;
if(angleX < 0) angleX += 360;
RenderScene();
}
document.onkeydown = function(e)
{
if(e.keyCode == 37) leftKeyDown = true;
if(e.keyCode == 39) rightKeyDown = true;
if(e.keyCode == 38) upKeyDown = true;
if(e.keyCode == 40) downKeyDown = true;
}
document.onkeyup = function(e)
{
if(e.keyCode == 37) leftKeyDown = false;
if(e.keyCode == 39) rightKeyDown = false;
if(e.keyCode == 38) upKeyDown = false;
if(e.keyCode == 40) downKeyDown = false;
}
function Init()
{
var myCanvasObject = document.getElementById('myCanvas');
webgl = myCanvasObject.getContext("experimental-webgl");
webgl.viewport(0, 0, myCanvasObject.clientWidth, myCanvasObject.clientHeight);
vertexShaderObject = webgl.createShader(webgl.VERTEX_SHADER);
fragmentShaderObject = webgl.createShader(webgl.FRAGMENT_SHADER);
webgl.shaderSource(vertexShaderObject, ShaderSourceFromScript("shader-vs"));
webgl.shaderSource(fragmentShaderObject, ShaderSourceFromScript("shader-fs"));
webgl.compileShader(vertexShaderObject);
webgl.compileShader(fragmentShaderObject);
if(!webgl.getShaderParameter(vertexShaderObject, webgl.COMPILE_STATUS)){alert(webgl.getShaderInfoLog(vertexShaderObject));return;}
if(!webgl.getShaderParameter(fragmentShaderObject, webgl.COMPILE_STATUS)){alert(webgl.getShaderInfoLog(fragmentShaderObject));return;}
programObject = webgl.createProgram();
webgl.attachShader(programObject, vertexShaderObject);
webgl.attachShader(programObject, fragmentShaderObject);
webgl.bindAttribLocation(programObject, v3PositionIndex, "v3Position");
webgl.bindAttribLocation(programObject, cubeTexSTIndex, "v2CubeTexST");
webgl.linkProgram(programObject);
if(!webgl.getProgramParameter(programObject, webgl.LINK_STATUS)){alert(webgl.getProgramInfoLog(programObject));return;}
samplerIndex = webgl.getUniformLocation(programObject, "s_texture");
um4RotateIndex = webgl.getUniformLocation(programObject, "um4Rotate");
webgl.useProgram(programObject);
if(LoadData() != 0){alert("error:LoadData()!");return;}
window.setInterval("RotateTriangle()", interval);
}
</script>
</head>
<body onload='Init()'>
<canvas id="myCanvas" style="border:1px solid red;" width='600px' height='450px'></canvas>
<img id="myTexture" src='texture.bmp'>
</body>
</html>
运行起来之后，发现贴图上有些问题，可能是我使用的FF浏览器的bug。