I'd like to implement an algorithm about pencil rendering. Now I've got 32 textures with different stroke intensity and some models. The process goes like this. First, I should render the using Phong shading to determine the intensity. Then I should map the texture to the rendered result.
The textures should be stored in 3d texture space. The problem is that I don't know how to do multipass rendering with opengl and shaders. And I don't know how to access to the textures with the right coordinate. What if the faces of the mesh is smaller than the texture? Can anybody show me some examples of doint this?
You need to render to some sort of offscreen buffer in order to do multi-pass rendering.
Framebuffersare the current method of doing offscreen rendering in OpenGL. Apple has a good page describing how to use them. (It's not Mac-specific.)I'm not sure I understand your question about texturing, so can't answer that part.