One technique for texturing terrain I’ve seen used is the use of seperate textures which are blended together using a larger “blend map,” or terrain attributes (slope, altitude, etc). For example: Different areas of a landscape can be dirt, snow or grass, and the textures are blended together at their edges. I have managed to do something like this using multipass techniques, but it’s much too slow to be of practical use. For one thing, it requires that the scene be transformed once for each pass (is there a way around that, at least?)
I’m very willing to settle on one rule: No more than two textures can exist on the same face or vertex. That is, snow can blend to rock, and rock can blend to grass, but snow, grass, and rock cannot blend together over one face. The add-on to Quake III Arena, Team Arena, supports terrains that follow these same rules. An entirely different game, Earth 2150, also uses similar techniques for rendering terrain. Actually, I was just browsing my “Downloads” directory, and it seems that an amateur coder’s engine, “Heylow,” also uses this technique. Too bad he didn’t release any source!
I have seen how multiple texture units of a video card can be used to perform multitexturing specifically with lightmaps, but I have not seen anything regarding alpha multitexturing, but I assume this just requires the use of an RGBA texture. And I assume these games use alpha channels in some manner. But each texture’s alpha map appears, at least, to be of a much lower resolution than the actual texture. The alpha map is stretched over the entire terrain, while the texture map is tiled.
Hopefully I have described my goal well enough. Does anyone have any idea as to how I could reach it? If I could use multitexturing, I would for obvious reasons prefer that approach.
[This message has been edited by TerranFury (edited 09-02-2001).]