Wrong calculation of rolling resistance

[LBodnar]

I have noticed two problems with GetRollingResistance:

Firstly, calculation in cartyre.cpp does not include normal force Fz.
Rolling resistance is approximated by

Code:

Fr = - f * Fz

where Fz is normal force in Newtons and f is

Code:

f = fo + KV^2

where V is vehicle velocity in m/s.

GetRollingResistance function does not include Fz which makes it off by a factor of 4000-5000. E.g. with "rolling-resistance = 1.3e-2, 6.5e-6" at standstill the resistance returns 0.013 N which is 1 milligram * force. Multiplying it by 4500N we get more realistic 60N or 6 kg*f per tyre.

Secondly, it is called from cardynamics.cpp with a wrong argument:

Code:

btScalar rolling_resistance = - tire[i].GetRollingResistance(wheel[i].GetAngularVelocity(), ...);

this should be longitudinal velocity, not angular.

Thanks
Leo