   Map editor / Scenegraph
  DirectX newbie question:I''m making a space-shooter with DirectX 9. I''ve made a simple custom level editor that basically arranges polygons (quads/tris) and lines (used for object/world collision detection). I wan''t the levels to be reasonably big, so I''m going with a BSP tree where the nodes are split by either perfectly horizontal or vertical lines. (The world will be made up of 3d objects and quasi-3d ''walls'', but the gameplay and physics is essentially 2d). When I split a node, it''s perfectly down the middle, with each node having at most 2 children. My initial reason for this was culling during collision detection (lots of objects, and possibly lots of ''lines'' to check against). Obviously, I''d want to throw the polygon information in there as well, to speed up rendering. My question is, what''s the best way for the rendering system (DirectX 9) to fit in with the scene graph? Do I have a vertex buffer per bsp node/leaf? What''s the min/max # of polygons you should add to a vertex buffer? How much of an advantage are indexed primitives?Any help would be much appreciated!! 