If we are talking about 3D outdoor maps using heightmaps, rendering is made faster using either GeoMipmaps (easy to implement) or GeoClipmaps (fastest).
Collision detection is made faster by taking advantage of the uniform structure of a heightmap, but if you want specifics you will have to ask, since I am not even sure I am answering your vague question.

If we are talking about indoor buildings, rendering speed is improved via PVS’s and collision detection is improved via octrees and BVH’s.

You will need to be more specific if you want more-specific details.


L. Spiro

Are you talking 2D or 3D? What type of game are you working with? If you can get away with it, using a plain grid is always really fast!