尹曦正写实CG绘画网课班-第十期
继承Image，重写IsRaycastLocationValid方法，利用PolygonCollider2D自定义按钮的点击区域。
using UnityEngine;using UnityEngine.UI;public class PolygonImage : Image{
private Collider2D _collider2D = null;
private Collider2D UICollider2D {
get
{
if (_collider2D == null)
_collider2D = GetComponent<Collider2D>();
return _collider2D;
}
}
#region 优化 (透明的Image 也会持续的早成绘制的开销。)
protected PolygonImage()
{
useLegacyMeshGeneration = true;
raycastTarget = false;//默认关闭射线检测
