A plane is two actual triangles which make up a sqaure. Perfect for billboarding trees and it uses very little polygons. I haven't found the capability in BSP yet. A plane is not a box, it's only two sides. Therefore, if I textured a tree texture on a plane, and made 4 of them in a star shape, it makes a really good looking tree. Good looking considering what we're dealing with in terms of polys, etc. If you've done 3D modelling like I have, you'll understand the concept.