[ODE] FDir1 and Slip for car wheels

[Jon Watte]

> I've also tried dContactSlip2 flag as explained in the documentation.
> Although it helps in making the car to skid instead of flipping over, I'm
> not satisfied with the results (it makes the car to behave a little like a
> hovercraft).

Things to try:


Even lower center of gravity -- note: this means your actual body is low, 
and the geom is offset upwards. dMassTranslate() is ignored by the body 
solver.


Sway bars -- when the left strut compresses, add a compression force on 
the right strut, and a corresponding de-compression force on the left 
strut.


Enable dContactApprox1 -- else mu is just a force limiter, rather than a 
normal multiplier.


Tune the slip constant. A small slip constant of about 0.01 ought to be 
sufficient. Too much, and you get too much slippage (like you seem to be 
having).


You can get the carworld demo and see the wheeled vehicle in that from 
http://www.mindcontrol.org/~hplus/carworld/

If that still doesn't give you the car you want, you probably want to go 
with a single box, and four rays for suspension, plus some friction-less 
contact area (spheres or ccylinders) for bottoming out. The "tank" in 
carworld is built like that.

Cheers,

			/ h+