为webgl中的每个对象使用不同的顶点和片段着色器 [英] Using a different vertex and fragment shader for each object in webgl

问题描述

我在webgl中有一个包含多个对象的场景。对于每个对象，我想使用不同的顶点和片段着色器。我的第一个问题是，是否可以为每个对象设置着色器？我知道在opengl中是可能的。

I have a scene with multiple objects in webgl. For each object I want to use a different vertex and a fragment shader. My first question is, is it possible to have a shader for each object? I am aware it is possible in opengl.

这是我想到的类似伪代码。任何例子都将非常感激。

This is something similar pseudo code of what I had in mind. Any example would be much appreciated.

glenableshader
draw triangle
gldisableshader

glenableshader
draw square
gldisableshader

谢谢

推荐答案

您可以查找几乎任何WebGL示例并将其转换为多个着色器示例。

You can look up pretty much any WebGL example and turn it into a multiple shader example.

伪代码

// At init time
for each shader program
    create and compile vertex shader
    create and compile fragment shader
    create program and attach shaders
    link program
    record locations of attributes and uniforms

for each model/set of geometry/points/data 
    create buffer(s) for model
    copy data into buffer(s) for model

for each texture
    create texture
    usually asynchronously load textures

// at draw time
clear

for each model
   useProgram(program for model)
   setup attributes for model
   setup textures for model
   set uniforms for model
   draw

这与使用1个着色器程序绘制1个模型没什么不同。只需进行相同的设置。

This is no different than drawing 1 model with 1 shader program. Just do the same setup.

多一点代码...

设置属性会看起来像什么喜欢

For setting up attributes would look something like

for each attribute used by model
   gl.enableVertexAttribArray(attribLocation);
   gl.bindBuffer(gl.ARRAY_BUFFER, bufferWithDataForAttribute);
   gl.vertexAttribPointer(attribLocation, ...);

设置纹理（可能）看起来有点谎言

Setting up textures (might) look something liek this

for each texture used by model
   gl.activeTexture(gl.TEXTURE0 + ndx);
   gl.bindTexture(gl.TEXTURE_2D, texture);

最后你要使用的程序

gl.useProgram(programForModel);
for each uniform
   gl.uniform???(uniformLocation, uniformValue);

gl.drawArrays(...) 
or 
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, bufferOfIndicesForModel);
gl.drawElements(...);

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