In games like unrealtournament 2003, i noticed that the terrains had area where the terrain went inwards... with a normal terrain map, you can only have hills since you only have one layer in the raw file. Is this what is known as voxels? I know how to do some volume rendering (ie make a box with a volume) but how is a terrain made like that?

Games like UT don''t use height maps. The levels are hand-build (mesh by mesh) and are generally stored in BSP (binary space partitioning) format. You can''t (easily) have caves and such in a simple heightmap engine.

Crispy

you can use height maps for ground and scene like buildings for caves mountains and cliffs. (use a model and draw it over the height map.

UT 2003 uses a height map for the actual terrain and then inserts objects like rocks, trees, ect (called static meshes), for any non-terrain/non-bsp elements.

If you use a heightmap with X,Y and Z values, you can offset the X and Z values to create overhangs (not caves though). This would best be done visually in some kind of editor.

Thanx alot, that really helped. I wasnt sure aout that stuff, i remember reading before about terrain editors, i just though that they were specialized paint programs, lol.