public unsafe static void SetAnisotropicFriction(this CollisionObject obj, ref OpenTK.Vector3 anisotropicFriction)
 {
     fixed(OpenTK.Vector3 *anisotropicFrictionPtr = &anisotropicFriction)
     {
         obj.SetAnisotropicFriction(ref *(BulletSharp.Math.Vector3 *)anisotropicFrictionPtr);
     }
 }