[ODE] Collision objects

[Tim Schmidt]

> so ignores the collision.  Your case is a little trickier, as you'll have
to
> lookup the objects in a table or something of the kind to determine if
it's
> one of your invisible objects, but certainly not a insurmountable problem.

I had the same problem, because I needed contact sensors for some neuronal
net controlled objects.
You can use (or maybe misuse ;-) ) the dGeomSetData/dGeomGetData functions
to mark your objects as non-collidable.

    Tim