Well I hadn't thought of the sun vector that way, but that is great advice-- should certainly speed things up, a little at least. As for the number of faces...I'd like to take a surface and run it with arbitrary granularity; so, thousands. Running my code as it stands for 1000 faces takes on the order of 15 minutes to run. Making the change you suggested now...

@adamb said: @thomthom said: @adamb said: But if you like, I've got code that handles quads Quads? Whatcha mean? You give me a four-sided polygon (quadrilateral) , and I'm sure I can stretch to writing code to break it into triangles. Best response ever.