[ODE] Contrib modules

[Aras Pranckevicius]

> 1. TerrainAndCone
> Is there any reason why I should use Terrain module when there 
> exists TriMesh implementation?

Several reasons (I'm just speculating - never used/examined terrain contrib) 
might be:

1. Efficiency. Terrain (heightfield) is more specialized case of triangle 
mesh; hence, you can do collision more efficiently (eg. for tri-mesh, you 
have to go down the AABB tree to reach colliding triangles; while for 
heightfield, you can get them nearly straight).

2. Solid-ness. (currently) Tri-meshes are just that - polygon soups. They 
have no interior, no adjacency information, just a bunch of triangles. 
Terrain, on the other hand, has implicit adjacency; and a "inside" 
and "outside" parts (so, anything deeply beneath it's surface is colliding; 
while with tri-meshes, it wouldn't be).

3. Exactness (partly from 2nd point) - finding collision depth/point/normal 
from just triangle soup is very very hard. Current ODE's implementation for 
TriMesh is just an approximation; while terrain implicitly has some extra 
useful info (adjacency and "inside-outside").


Aras Pranckevicius aka NeARAZ
http://www.gim.ktu.lt/nesnausk/nearaz/