Point Inside Polygon

点在多边形内判断算法

最新推荐文章于 2025-01-03 17:48:56 发布

原创最新推荐文章于 2025-01-03 17:48:56 发布 · 560 阅读

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本文介绍了一种常见的判断点是否位于多边形内部的方法。通过水平射线法来确定点与多边形的关系，该算法适用于任意数量顶点的多边形。文章还讨论了射线与多边形边相交的特殊情况。

Here is the most known method to test if point is inside polygon.

p polygon
n number of vertices in polygon
q point

RightHorizontalRayIntersection(q,u,v) tests if horizontal ray starting from point q (in right direction) intersects a segment (u,v).

Code:

bool IsPointInsidePolygon( P *p,int n,P q ) {
int i,j,c=0;
for (i=0,j=n-1; i<n; j=i++) // Considering all segments (p[i],p[j])
if (RightHorizontalRayIntersection( q,p[i],p[j] )) c++;
return c%2;
}

There is a special cases, ray r intersects a segment in one of it.

Sample:

http://blog.youkuaiyun.com/xqls_xqls/archive/2009/07/30/4393369.aspx