Bullet sets the wheel contact normal in btVehicleRaycaster::castRay.
I derive from btVehicleRaycaster and override that method ...
How do you determine which vertices to use?
I assume the data must be somewhere in either the btRigidBody or the btVehicleRaycasterResult ?
Generally, since the vehicles are heavy & slow-moving, perhaps you'll get better result using rigid body wheels instead of ray cast.
In my own experiments, rigid body wheels have quite big advantages over raycast in terms of being realistic. But since things usually breaks apart physics-wise at high speed (rotations) and require more processing power, raycast usually is better suited for racing-type games... But your choice of vehicles implies that this is not racing
true. But processor power IS a concern. Hence, we're trying raycast vehicles first.
@kester: Thanks! That triangle index is what I was looking for.