///User can override this material combiner by implementing gContactAddedCallback and setting body0->m_collisionFlags |= btCollisionObject::customMaterialCallback;
private float CalculateCombinedFriction(CollisionObject body0,CollisionObject body1)
{
float friction = body0.GetFriction() * body1.GetFriction();
const float MAX_FRICTION = 10f;
if (friction < -MAX_FRICTION)
friction = -MAX_FRICTION;
if (friction > MAX_FRICTION)
friction = MAX_FRICTION;
return friction;
}