Ok, here''s my thoughts. I''m really looking for people to tell me if this will work, and if not why not. Saves time in the long run, and I''m interested to see how people reason these things. Suppose I was writing an engine for a game, and I wanted it to be as general as possible. I want to handle indoor environments and outdoor, with some ''levels'' being a mixture of the two. I want the mixtures to be seamless, so the way I was thinking of handling this would be to have an Area class, so the level could be split into indoor areas and outdoor areas, separated by portals. Each area would have its own HSR algorithm from a list of pre-implemented ones, say quadtrees for outdoor and PVS for indoor or whatever, and you can freely look through the portals (eg doors, windows) into the other areas. Right, would this work? Is there a better, more efficient way of handling this? Am I just stupid? Your thoughts please! -- Sartori "What is now real was once only imagined..."