3D layers visualization

wanna know how to create 3D visualization of layers of materials, for instance i want to diaplay a structure containing 2 layers where the 2nd layer (on top of 1st layer) follows the suface shape of curve of the 1st layer?(ie the 2nd layer is not flat)

how about rendering the 2nd layer flat to an area, say 512x512 pixels. (use glViewport). If this is renderered to the back buffer only, it can then be read into a texture. You could then set the display to the full viewport size and render the 1st layer as geometry and apply the 2nd as a texture?

This kinda depends on exactly what you mean by rendering layers? of course I could just be misunderstanding and you may be simply asking about blending (look up glBlend() ), but then I don’t know without more info…