[ODE] Read friction forces?

[Amund Børsand]

Is there an easy way to find out how much force is applied to a body
through friction? I.e. not the normal forces that carry the object (I am
making a vehicle simulation, I'm talking about a wheel standing on the
ground), but only the forces that act normal to the surface it's sitting
on. If it were to be on plain ground this would be simple, but I'm going
to be running over other geoms, several at the same time probably. I
would need another friction model soon (Pajecka or something similar),
is there some easy place to implement this? Could it somehow be plugged
into ODE and be used instead of the standard friction models, while
still letting normal collision detection and contact forces remain?

Also, I'm not sure how to implement my differentials, this is really
what I'm trying to do by reading the friction forces.. but I'm not sure
that will work. What would be perfect would be to have a sort of an
"input" hinge on the front of the axle to which I connect my driveshaft,
which would then distribute the forces to the two wheels. Could it be
possible to implement such a joint, or to program it somehow? My problem
is that the forces have to go both ways.

-- 
Amund Børsand <amund £ offroad . no>