Concave brushes are not allowed because of what Corvidae mentioned. OpenGL and Direct3D, and the math routines used in software rendering all fuss up with concave polygons. Sometime's they'll draw properly, most times they wont. As you mentioned, it's a simple process to split them up (tessellate mr. big-time lingo :) ) into triangles, since it essentially renders (no pun intended) the same effect.
david -----Original Message----- From: Reedbeta [mailto:[EMAIL PROTECTED]] Sent: Wednesday, December 19, 2001 11:54 PM To: [EMAIL PROTECTED] Subject: RE: [hlcoders] Concave objects? > > Why aren't concave brushes allowed, anyway? > > Simply put, concave polygons are very difficult to deal with in the > rendering pipeline. It's infinately more efficient to tesselate them into > triangles (which are always convex). While some engine might let you have > concave brushes, it would need to tesselate them when it came time to > process/render them. > > Plus, it's a basic assumption that allows the whole BSP approach to work. =) BSP does require the visible level space to be partitioned into convex polyhedra (or "leaves" as they're called), but there's nothing particularly bad about having concave brushes. After all, it's simple to split them into multiple convex brushes during compile time. I think the main problem with concave brushes is that they cannot be displayed in the map editor without great difficulty. The polygons of a convex brush do not need to be depth-sorted (although back faces need to be culled), whereas the polygons of a concave brush do. __________________________________________________ Do You Yahoo!? Check out Yahoo! Shopping and Yahoo! Auctions for all of your unique holiday gifts! Buy at http://shopping.yahoo.com or bid at http://auctions.yahoo.com _______________________________________________ To unsubscribe, edit your list preferences, or view the list archives, please visit: http://list.valvesoftware.com/mailman/listinfo/hlcoders _______________________________________________ To unsubscribe, edit your list preferences, or view the list archives, please visit: http://list.valvesoftware.com/mailman/listinfo/hlcoders
