public static void DeleteAndDisposeAllRigidBodies(this DynamicsWorld world)
 {
     for (int i = 0; i < world.NumCollisionObjects; i++)
     {
         CollisionObject obj  = world.CollisionObjectArray[i];
         RigidBody       body = obj as RigidBody;
         world.DeleteAndDisposeBody(body);
     }
 }