[ODE] Stabilizing cars (finally!)

[Jon Watte]

> The solution turned out to be extremely low tech : after each time step, 
> if the car is not airborne (ie at least one wheel touches the ground), 
> I do dBodyAddRelForce(getChassisObject()->getBody(), 0, -5000, 0). This 
> essentially makes the car stickier to the road. The -5000 value is arbitrary  
 
Thanks for the note to the list!

I actually have something similar, but I apply it in the "DOWN" direction 
of the car's body, and I always apply it (not just when in contact), and 
it's proportional to velocity, and I call it "AIR_SUCK" -- it's the 
general aerodynamical down-force that fast cars are designed to exert on 
the wheels. If you don't already have this yourself, that's probably what 
you actually end up modeling, except your model is unorthodox :-)

The other big winner is sinking the center of gravity of the main chassis. 
Because the dMass mass offset IS IGNORED by dBody, this means that you 
have to sink the entire dBody, and then offset the box/boxes upwards again 
to compensate. However, this makes for much less roll-y cars.

Cheers,

			/ h+