I have the general idea that OCtree is good for outdoor scenes and BSP for indoor scenes. But what to use for a hybrid scene that has both outdoor and indoor scenes to render? Let me give some some real examples: a) Serious Sam, b) Unreal II. Both games renders indoor scenes and outdoor scenes with farely large terrains/mountains/castles/buildings etc. Serious sam obviously didn''t use precompiled BSP; and as i know Unreal Engine uses BSP, that means Unreal II used bsp as well and rendered some huge outdoor scenes (desert, hilly terrain) as well. What i would like to know is when we have both indoor and outdoor scenes to render in a same level which parititioning technique is best to use?

not sure where i have read it but i think yann said it
that you should use octree for in and outdoor

nowadays these extra polygons don t matter anymore

rendering a BSP tree takes longer than rendering the entire indoor area with one big vertex array

but you can still make use of PVS

I just found something interesting on http://udn.epicgames.com/pub/Content/LevelOptimization/
The zone based BSP doens''t work very well on outdoors, because its difficult to specify portals, so they use ''Antiportals'' (invisible barriers used for blocking geometry from the renderers view). Any idea how to implement this with BSP?
Can it be used in an Octree? because with octree if i am looking at a hill and their is something at the other side of the hill, they are rendered , obviously 3D games have big value for the ''far'' clipping plane and many objects blocked from view can be rendered for appearing inside the viewing frustrum..

Modern hardware speeds and CPU/GPU parallelization capabilities suggest that you can acvhiece the best results by using Octrees and software Hierarchial Occlusion Maps (HOMs) for any kind of geometry. This has the following benefits:
- One algorithm for all scenes.
- Your artists are free to design any kind of level they wish. They have no artificial restriction to do dungeon-style indoor levels and completely bare outdoor ones.
- You take good advantage of CPU/GPU parallelization and get HOMs practically for free.

Search the forums, Yann gave an excellent explanation above this earlier.