[ODE] FDir1 and Slip for car wheels

[Arturo Colorado Garín]

>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.

It begins to be too evident how low the center of mass is (for example when
rotating in the air) so I can't lower it even more.


>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.

This is not too real, is it? I would like to stick to reality as much as
possible. However it sounds like it helps a lot in stabilizing the car so
I'll probably give it a try.


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

Already enabled.


>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).

I set the slip constant in each step to 0.0001 times the wheel linear
velocity so it is already small enough.


I still think (hope) FDir1 can help with this. Has anybody used it?

Thx!

--Arturo Colorado