public static class HeightfieldCollisionShape
Uses Bullet Physics Heightfield terrain collision system. This is MUCH faster
than using a regular mesh.
There are a couple tricks though:
-No rotation or translation is supported.
-The collision bbox must be centered around 0,0,0 with the height above and below the y-axis being
equal on either side. If not, the whole collision box is shifted vertically and things don't collide
as they should.