UI 相機的可見區域之外，雖然會被顯示卡繪製剪裁掉，但是會消耗drawcall。我們可以利用AABB碰撞檢測剔除掉，相機之外的ui元素，就是active false掉。效果如下：

this.planes = GeometryUtility.CalculateFrustumPlanes(this.uiCamera);

using System;
using UnityEngine;
using UnityEngine.UI;
using UnityEngine.EventSystems;
using System.Collections;


namespace Framework
{
	public class RenderTestVisible : MonoBehaviour
	{
		private PolygonCollider2D box;

		public GameObject firstChild;

		void Start()
		{
			this.box = this.GetComponent<PolygonCollider2D>();

			if (this.firstChild == null)
			{
				this.firstChild = this.gameObject;
			}

			ACoroutineManager.StartCoroutineTask(Check());
		}


		IEnumerator Check()
		{
			while (true)
			{
				if (this == null)
				{
					yield break;
				}
				else 
				{
					if (GeometryUtility.TestPlanesAABB(AUIManager.instance.planes, this.box.bounds))
					{
						this.firstChild.SetActive(true);
					}
					else
					{
						this.firstChild.SetActive(false);
					}

					yield return 5;
				}
			}
		}
	}
}
 

• 使用GeometryUtility.CalculateFrustumPlanes獲得ui相機的平面
• 使用GeometryUtility.TestPlanesAABB判斷碰撞
• 使用PolygonCollider2D來和攝像機檢測碰撞
• 需要動態檢測的ui上掛載，PolygonCollider2D元件和RenderTestVisible元件
• RenderTestVisible上GameObject是需要動態active變化的物件
  
• yield return 5 是每5幀進行一次碰撞檢測