Wow, I though IO was going to have time to put to work on the plugin, but I spend all on the vehicle and the skeleton solver.
On the vehicle I add a more realistic engine, now the engine internal friction loses are modeled with dry function. I also fix a bug in the calculation the lateral friction.
The car will be slightly but this the correct thing to do, because it feel more realistic.
I was able to do tire doughnut and tire burn out.
to do tire Doughnut you move forward and we the RPM the point where is going to change gear, tap the hand break while turning.
at this print you can try to correct by turning there tire the other way ( this is still too lose, but start to show sigh of proper simulation)
If you turn the tires to the same direction of the spin, the car do a perfect Doughnut at about 30 kmh.
The cool thing, is that the Doughnut is maintain even if you straight the tire,
I see if I can make a video.
here you can observe how important the differential is, the pivot tire is impost to spinning at all, while all other tires spins a different rate.
if you turn the tire to the opposite direction the you get out of the Doughnut.
I was also able to drift, but I could no control it yet.
at these point the there are two more features, left before plugging the traction control.
the tire integration required a sun sampling, specially when the are near the goring of the tire friction model. Basically the stiffness f the friction model is too strong and a very small change in slip ratios causes huge forces longitudinal and laterals forces and the tire RMP tend to overshot.
once we have that the we add the traction control so that Tire so not spin more that 2 maybe tree time the velocity of the tire center.
and finally lateral dynamic for controlled drifting, and high speed cruising.
we are getting very close to the final here.