Gets ground collision data for the wheel.
If the wheel collides with something, returns
true and fills the
hit structure. If the wheel
is not colliding, returns
false and leaves
hit structure unchanged.
The reported hit is always the closest one. Because the tire friction model does not automatically respond to other PhysicMaterials, any simulation of different ground materials must be done manually by adjusting forwardFriction and sidewaysFriction based on collider's material returned here.