private void UpdatePhysicsElement()
            {
                if (!Solid)
                {
                    deletePhysicsElement();
                    return;
                }
                if (Static)
                {
                    if (dynamicPhysicsElement != null)
                    {
                        deletePhysicsElement();
                    }
                    else if (staticPhysicsElement != null && staticPhysicsElement.Mesh != Mesh)
                    {
                        deletePhysicsElement();
                    }
                }
                else
                {
                    if (staticPhysicsElement != null)
                    {
                        deletePhysicsElement();
                    }
                    else if (dynamicPhysicsElement != null && dynamicPhysicsElement.Mesh != Mesh)
                    {
                        deletePhysicsElement();
                    }
                }

                if (Mesh == null)
                {
                    return;
                }

                if (Static)
                {
                    if (staticPhysicsElement == null)
                    {
                        staticPhysicsElement = factory.CreateStaticElement(Mesh, Entity.WorldMatrix.xna());
                    }
                    staticPhysicsElement.ActorUserData = this;
                }
                else
                {
                    if (dynamicPhysicsElement == null)
                    {
                        dynamicPhysicsElement = factory.CreateDynamicElement(Mesh, Entity.WorldMatrix.xna());
                    }
                    dynamicPhysicsElement.ActorUserData = this;
                }
            }
 private void deletePhysicsElement()
 {
     if (staticPhysicsElement != null)
     {
         factory.DeleteStaticElement(staticPhysicsElement);
         staticPhysicsElement = null;
     }
     if (dynamicPhysicsElement != null)
     {
         factory.DeleteDynamicElement(dynamicPhysicsElement);
         dynamicPhysicsElement = null;
     }
 }