[ODE] Simple beginner's questions (dGeomIDs in dContactGeom)

[Chris Campbell]

> collision detection system can be used ...', then why must I 
> fill in a dGeomID to the dContactGeom structure rather than a 
> dBodyID? Given that I have no interest whatsoever in using 

I wondered about this too... just make the geom id zero, it seems to work.
The important one is dJointAttach, which is where the joint and the body are
associated with each other. I'm still not really sure why dContactGeom has
dGeomId members... ?