Fix issue 925 (wheel rotation calculation)

[tomo0613]

#925

explanation (by Claude):

The Bug
In src/control/ray_cast_vehicle_controller.rs, the wheel rotation update uses a fwd (forward) vector computed independently from the chassis rotation:

let mut fwd = chassis.position().rotation * Vector::ith(self.index_forward_axis, 1.0);
let proj = fwd.dot(wheel.raycast_info.contact_normal_ws);
fwd -= wheel.raycast_info.contact_normal_ws * proj;

But the friction impulse system in update_friction() computes forward as:

self.forward_ws[i] = surf_normal_ws.cross(self.axle[i]).normalize_or_zero();

These two methods produce vectors that can point in opposite directions depending on the axle axis convention. For example, with index_forward_axis = 2 (Z forward) and a wheel axle along -X:

• forward_ws[i] = Y × (-X) = -Z
• fwd = +Z ← exact opposite!

The result: delta_rotation has the wrong sign, making the wheel appear to spin backward (and it cancels out to ~0). When steering is applied, the axle rotates, which partially corrupts/corrects the mismatch — which is exactly why rotation only appears when steering.

[tomo0613]

video evidence of the bug:

offroadJS_v2.rapier_current.mp4

and the fix:

offroadJS_v2.rapier_fixed.mp4

[tomo0613]

As I was testing, found out that the fix is not complete.
better than before ( video evidence :) ), but;
no rotation when wheels in the air and should spin
and wheels can NOT lock when braking

I'm comparing the ccde to cannon-es (also bullet port), and will update this PR

[tomo0613]

I added 2 extra conditions based on cannon-es implementation.
https://github.com/pmndrs/cannon-es/blob/master/src/objects/RaycastVehicle.ts

this handles if a wheel should start spinning (if wheel in air and engine force is applied, or on ground but looses grip while engine force is applied [burnout]):

      if ((wheel.sliding || !wheel.isInContact) && wheel.engineForce !== 0 && wheel.useCustomSlidingRotationalSpeed) {
        // Apply custom rotation when accelerating and sliding
        wheel.deltaRotation = (wheel.engineForce > 0 ? 1 : -1) * wheel.customSlidingRotationalSpeed * timeStep
      }

this handles if a wheel should stop spinning:

      // Lock wheels
      if (Math.abs(wheel.brake) > Math.abs(wheel.engineForce)) {
        wheel.deltaRotation = 0
      }

I also checked ammo.js and these issues are there as well
https://github.com/kripken/ammo.js/