/// <summary>
        /// 回收所有场景元素到对象池并清空集合。
        /// </summary>
        public override void Clear()
        {
            for (int i = 0; i < elements.Count; i++)
            {
                SceneElementPool.Delete(elements[i]);
            }

            elements.Clear();
            elementCoordinates.Clear();
        }
        protected override void UpdateCulling(ALayerCamera layerCamera)
        {
            if (elementCoordinates.Count == 0)
            {
                return;
            }

            // 获取可见的最近和最远场景元素的索引值
            int nearElementIndex;
            int farElementIndex;

            GetVisibleElementsRange(layerCamera, out nearElementIndex, out farElementIndex);

            // 设置可视范围内的元素为可见
            for (int i = nearElementIndex; i <= farElementIndex; i++)
            {
                if (!elements[i].IsVisible)
                {
                    elements[i].OnBecameVisible(layerCamera);
                }
            }

            // 回收身后的场景元素
            if (positiveDirection == RelativeDirection.Positive)
            {
                int index = 0;

                while (index < nearElementIndex)
                {
                    SceneElementPool.Delete(elements[0]);
                    elements.RemoveAt(0);
                    elementCoordinates.RemoveAt(0);
                    index += 1;
                }
            }
            else
            {
                int index = elements.Count - 1;

                while (index > farElementIndex)
                {
                    SceneElementPool.Delete(elements[index]);
                    elements.RemoveAt(index);
                    elementCoordinates.RemoveAt(index);
                    index -= 1;
                }
            }
        }