Oh, checker, I see. Now as you say it, it is obvious (even for me :-)).
Thanks for the code.
What do you want to do with it? Wouldn't it be better to rotate the marble
by 90 degree? In that way the colour get darker when they go "deeper". If
you want to use it as a normal, a heightfield or an isosurface-function, the
don't know if it is as easy as it sounds.
Marc-Hendrik
