Maurice, - Thanks a lot for the excellent tutorials! If I ever make it big with an app, I'll be sure to donate for your dedication!
For tutorial 8 (labeled 7), I noticed what I think is an error. You say the normal vector is perpendicular to the plane which the vertices make up:
Shouldn't the normal vector point in the opposite direction here? The vertices are going in a clockwise direction, 0 -> 1 -> 2 and by the right-hand rule, the normal should be opposite.
