public void OnPointerUp(PointerEventData eventData)
        {
            if (enableMultiTouch || activePointers.Count == 0)
            {
                List <ITapReceiver> pointerDownReceivers;
                if (useCircleCast)
                {
                    pointerDownReceivers = InputToCircleCast <ITapReceiver>(eventData.position, circleCastRadius);
                }
                else
                {
                    pointerDownReceivers = InputToRaycast <ITapReceiver>(eventData.position);
                }

                /*
                 * for (int i = 0; i < pointerDownReceivers.Count; i++)
                 *  pointerDownReceivers[i].OnPointerUp(position);
                 */

                ITapReceiver tapReceiver = GetCloserObject(pointerDownReceivers);
                tapReceiver?.OnPointerUp(position);
            }
            activePointers.Remove(eventData.pointerId);
        }