You can do soundmaps, they are great. You can do them in the sameway as shadowmaps, etc...
You make a 2D bitmap with color for every zone (green = grass, gray = asphalt, etc...). Then you must know the size of the 3d map and the size of the 2d map (both width and depth) and make a relation so one point in the 3d map is one point in the 2d map. After you test the rgb color of the x,y calculated in the 2d map and you use it.
I do this for my racing game, to get the shadows of the lightmap and the slip factor of the terrain and it works perfect!
Good Luck!
You make a 2D bitmap with color for every zone (green = grass, gray = asphalt, etc...). Then you must know the size of the 3d map and the size of the 2d map (both width and depth) and make a relation so one point in the 3d map is one point in the 2d map. After you test the rgb color of the x,y calculated in the 2d map and you use it.
I do this for my racing game, to get the shadows of the lightmap and the slip factor of the terrain and it works perfect!
Good Luck!