You know, if I would read the title of the post, I could answer my own question! Just saw your other posts about creating a formula driven shader for skin textures. Yes, the variables are as you describe them. The other variables you'll want to start playing with are these: nx, ny and nz; NX, NY and NZ. These are the variables that drive the Normalized vector for the point being shaded. I haven't played with forumlas in the capacity you are experimenting with. Keep us posted! Mark