shader=gl.createShader(gl.FRAGMENT_SHADER);
}elseif(shaderScript.type==”x-shader/x-vertex”){
shader=gl.createShader(gl.VERTEX_SHADER);
}else{
//Unknownshadertype
returnnull;
}
gl.shaderSource(shader,theSource);
//Compiletheshaderprogram
gl.compileShader(shader);
//Seeifitcompiledsuccessfully
if(!gl.getShaderParameter(shader,gl.COMPILE_STATUS)){
alert(“Anerroroccurredcompilingtheshaders:”+gl.getShaderInfoLog(shader));
returnnull;
}
returnshader;
}
步骤三：创建/加载模型数据 – initBuffers
这些小例子中，模型数据基本都是直接生成的，实际的程序中，这些数据应该都是从模型加载得到的：
复制代码
vartriangleVertexPositionBuffer;
vartriangleVertexColorBuffer;
functioninitBuffers(){
triangleVertexPositionBuffer=gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER,triangleVertexPositionBuffer);
varvertices=[
0.0,1.0,0.0,
-1.0,-1.0,0.0,
1.0,-1.0,0.0
];
gl.bufferData(gl.ARRAY_BUFFER,newFloat32Array(vertices),gl.STATIC_DRAW);
triangleVertexPositionBuffer.itemSize=3;
triangleVertexPositionBuffer.numItems=3;
triangleVertexColorBuffer=gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER,triangleVertexColorBuffer);
varcolors=[
1.0,0.0,0.0,1.0,
0.0,1.0,0.0,1.0,
0.0,0.0,1.0,1.0
];
gl.bufferData(gl.ARRAY_BUFFER,newFloat32Array(colors),gl.STATIC_DRAW);
triangleVertexColorBuffer.itemSize=4;
triangleVertexColorBuffer.numItems=3;
}
上面这段代码创建了三角形的顶点和顶点的颜色数据并放在缓冲区中。
步骤四：渲染 – drawScene
准备好了数据以后，交给WebGL去渲染就好了，这里调用的是gl.drawArrays方法。看代码：
复制代码
functiondrawScene(){
gl.viewport(0,0,gl.viewportWidth,gl.viewportHeight);
gl.clear(gl.COLOR_BUFFER_BIT|gl.DEPTH_BUFFER_BIT);
pMatrix=okMat4Proj(45.0,gl.viewportWidth/gl.viewportHeight,0.1,100.0);
mvMatrix=okMat4Trans(-1.5,0.0,-7.0);
gl.bindBuffer(gl.ARRAY_BUFFER,triangleVertexPositionBuffer);
gl.vertexAttribPointer(shaderProgram.vertexPositionAttribute,triangleVertexPositionBuffer.itemSize,gl.FLOAT,false,0,0);
gl.bindBuffer(gl.ARRAY_BUFFER,triangleVertexColorBuffer);
gl.vertexAttribPointer(shaderProgram.vertexColorAttribute,triangleVertexColorBuffer.itemSize,gl.FLOAT,false,0,0);
setMatrixUniforms();
gl.drawArrays(gl.TRIANGLES,0,triangleVertexPositionBuffer.numItems);
}
这个函数首先设置了3D世界的背景为黑色，然后设置投影矩阵，设置待绘制对象的位置，然后根据缓冲中的顶点和颜色数据，绘制对象。这里还有一些生成投影矩阵和模型视图矩形的辅助方法(使用了Oak3D图形库中的矩阵辅助方法)与主题关系不大，这里就不详细解释了。
