break up the levels in to smaller peaces... basically i had the same problem, I got around it by just using an array (uses lots of ram though)
imagine a cube, and your in the middle of that cube, the sector your in has 1 room, you show that where as you wont need to show the others around you as you move around the cube space the world hides and shows the objects closest to you in that cube
dim worldcube(255,255,255) holds the point to each mesh
this takes time to do though, but the result is a very fast level (only use alpha 0 and alpha 1 for hiding a showing cos this is faster AND objects on the other "cubes" will still need to check their positions and posible collisions
PHEW! i hope this helps?
imagine a cube, and your in the middle of that cube, the sector your in has 1 room, you show that where as you wont need to show the others around you as you move around the cube space the world hides and shows the objects closest to you in that cube
dim worldcube(255,255,255) holds the point to each mesh
this takes time to do though, but the result is a very fast level (only use alpha 0 and alpha 1 for hiding a showing cos this is faster AND objects on the other "cubes" will still need to check their positions and posible collisions
PHEW! i hope this helps?