参考

CGALDotNet快速开始：https://blog.csdn.net/liqian_ken/article/details/138274933

CGAL二维可视域计算介绍：https://doc.cgal.org/latest/Visibility_2/index.html#visibility_2_introduction
CGAL相关接口：https://doc.cgal.org/latest/Visibility_2/classCGAL_1_1Triangular__expansion__visibility__2.html

示例

已知多边形ABCDEFGHIJ，多边形内有一点视点K，下面要计算K点能看到的区域。

代码：

using CGALDotNet;
using CGALDotNet.Polygons;
using CGALDotNetGeometry.Numerics;
using System;
using System.Collections.Generic;
using System.Linq;namespace CTestCore31
{public class Program{static void Main(string[] args){var points = new Point2d[]{new Point2d(0, 0),new Point2d(0, 1),new Point2d(3, 1),new Point2d(3, 2),new Point2d(4, 2),new Point2d(4, 1),new Point2d(8, 1),new Point2d(8, -1),new Point2d(5, -1),new Point2d(4, 0),};points = points.Reverse().ToArray();var poly = new Polygon2<EEK>(points);var pv = new PolygonVisibility<EEK>();var pt = new Point2d(0.5, 0.5);pv.ComputeVisibility(pt, poly, out Polygon2<EEK> result);List<Point2d> resultPoints = new List<Point2d>();result.GetPoints(resultPoints);foreach (Point2d point in resultPoints){Console.WriteLine($"{point.x} {point.y}");}Console.ReadLine();}}
}

由此获得可视域多边形，其坐标：

3 1
0 1
0 0
4 0
8 -0.5714285714285714
8 1
4 1
4 1.2000000000000002

根据需要将其绘制出来，如下图所示：

将上面两张图叠加（绿色区域为视点K的可视域）：

注意

视点必须位于多边形内部，不能位于外部（计算结果为null）或多边形边界上（报错）。