Just a quick (and simple, I hope) question: Given four vertices and an x/y coordinate somewhere inside them, what would it take to figure out the altitude at that point? --------------- #define TRUE 0 #define FALSE 1 //MUAHAHAHAHAAAA!

I''m not sure that StrangeMonkey''s method works, but here is what I''d do (I hope it''s not the same thing he said): find the normal of the quad:

Normal = (A, B, C)

and plug it into the plane equation

Ax + By + Cz + D = 0

plug a (x,y,z) triple that''s part of the plane (any of the four vertices) to find D

D = -Ax - By - Cz

Then isolate y

Altitude = y = (-Ax - Cz - D) / B

It should be pretty fast (you don''t have to normalize anything), but I''m sure there is room for improvement.

Cédric