   Decals - Clipping Geometry
  Hi,I have a problem with decals. I have a ball shot at a wall and I get the Collision Point and the Normal Vector from PhysX, that is just fine.My Problem is now, that I need to clip the geometry against a cube, and I have absolute no idea how to do that.I have searched the forums and the net, but I may have used the wrong keywords.Thanks,Markus   
  You are using some ambiguous and undefined terms in your post.  For example, in the first line you have a wall and a ball, then in the next line there's a cube and some kind of generic geometry.  Also, what do you mean by "clip"?  Try to be a bit more clear.   ;  Well, ok, I am sorry, I try it again:I have a level and balls. The balls can move and collide with the level geometry. At collision I extract a Collision  Point and Normal Vector from Physx.With this I want to clip (crop) my level geometry, against 6 planes (this is what I ment by cube), so that I get a geometry for my decal to apply.If you still don't know what I mean yet: see http://blog.wolfire.com/2009/06/how-to-project-decals/So how do I do the clipping of my level geometry?I hope it was clear now, again SorryMarkus   ;  You can actually just skip the clipping step as long as your decal texture has transparent edges and you use clamp-mode instead of wrap-mode for that texture.   ;  The problem with this attempt is, that I have multiple decals on the level geometry, and applying it directly on the level geometry won't work.I forgot to add, that I copy the geometry of the level and want to remove everything outside this cube where the collision point is center.   ;  To check which triangles intersect the box, you can use any OBB vs triangle testing algorithm.What I meant was, that once you have this sub-set of triangles you don't have to clip them if you dont wan't to -- clipping is an optimisation to reduce the fill-rate overhead of your decals.   