public override void RemoveConstraint(Physic.Constraints.IPhysicConstraint ctn)
 {
     if (ctn is BulletConstraint)
     {
         BulletConstraint BulletConstraint = ctn as BulletConstraint;
         world.RemoveConstraint(BulletConstraint.Constraint);
     }
     ctns.Remove(ctn);
 }
 public override void AddConstraint(Physic.Constraints.IPhysicConstraint ctn)
 {
     if (ctn is BulletConstraint)
     {
         BulletConstraint BulletConstraint = ctn as BulletConstraint;
         world.AddConstraint(BulletConstraint.Constraint, BulletConstraint.DisableCollisionsBetweenLinkedBodies);
     }
     ctns.Add(ctn);
 }