I need some math help. The image may help you understand what I want. Basically, I want to be able to show a plane anywhere on the surface of a sphere. I have tried some methods, but I can't seem to get them to come out right. It is probably simple, but I can't get my head around it. The orientation of the plane needs to be such that "up" is always pointing toward the "north pole" of the sphere. Any ideas?