I have Panda’s portal culling system active in my game, and overall it seems to work rather well! However, I’ve hit an issue on which I’m uncertain of how to proceed, and would like to ask for help.
Specifically, how should I deal with objects that straddle a portal, and thus the bounds of two cells?
Right now, my cells don’t overlap–I honestly forget quite why I set it up so, but recall that I had a reason. Furthermore, I place my portal-quads just inside their destination cells, so that the camera’s near-plane doesn’t pass the portal before the camera enters its cell.
This means that there’s a gap between cells that I’m not sure of how to handle. Static level-geometry may simply be split across cells, but some objects–animated doors, or objects dropped by the player–are less prone to such treatment. In addition, the gap between cells means that objects placed there fail to detect a cell in which to be included.
One thought that occurs to me is to measure the camera’s position not from the camera-node’s location, but from a point in the centre of the near-plane, and to then allow cell-overlap and portals nearer the edges of their cells. I’m not confident that this will actually help, however.
So, any suggestions?
(I imagine that the use of portal-culling systems is fairly well-understood, given that portal-culling seems to be a fairly commonly-mentioned approach to culling. However, my searches for tutorials have thus far not turned up much: most seem to focus on the technical elements of portal-culling, not how to use it. :/)