OpenGL/GLSL -编写一个智能纹理着色器。

Let's say my texture is 256x256 pixel. It contains 16 sub-textures of 64x64 pixel. The sub-textures are to be rendered to quads. To increase performance I want to pass discrete values to the shader which encode per vertex texture coordinates. For example values 0, 1, 2, 3 should correspond to (0,64), (64,64), (64,0), (0,0) per vertex texture coordinates, etc.Let's say my texture is 256x256 pixel. It conta