[Unity算法]点是否在多边形范围内

参考链接：

https://www.zhihu.com/question/26551754

http://www.cnblogs.com/leoin2012/p/6425089.html

原理如下：

代码实现：

 using UnityEngine;
 using System.Collections.Generic;

 public class MathTool {

     /// <summary>
     /// 点是否在多边形范围内
     /// </summary>
     /// <param name="p">点</param>
     /// <param name="vertexs">多边形顶点列表</param>
     /// <returns></returns>
     public static bool IsPointInPolygon(Vector2 p, List<Vector2> vertexs)
     {
         int crossNum = ;
         int vertexCount = vertexs.Count;

         for (int i = ; i < vertexCount; i++)
         {
             Vector2 v1 = vertexs[i];
             Vector2 v2 = vertexs[(i + ) % vertexCount];

             if (((v1.y <= p.y) && (v2.y > p.y))
                 || ((v1.y > p.y) && (v2.y <= p.y)))
             {
                 if (p.x < v1.x + (p.y - v1.y) / (v2.y - v1.y) * (v2.x - v1.x))
                 {
                     crossNum += ;
                 }
             }
         }

         if (crossNum %  == )
         {
             return false;
         }
         else
         {
             return true;
         }
     }
 }