AutoCAD C# 多段线自相交检测

主要是通过 自身与自身进行“IntersectWith”操作，会返回端点及相交点。

思路来源：How do I know whether the polyline overlap itself? - Autodesk Community - AutoCAD

IntersectWith结果图：

 

#region 多段线自相交检测

        /// 

        /// 多段线自相交检测
        /// 
        /// 待检测多段线
        /// 返回自相交点集合
        /// 
        /// 
        public static bool SelfIntersectDetect(Polyline pPolyline, out List intersectPoint3Ds, out Exception error)
        {
            error = null;
            intersectPoint3Ds = new List();
            try
            {
                // 自身与自身相交结果（包含顶点和相交点）
                var intersectWithResult = new Point3dCollection();
                pPolyline.IntersectWith(pPolyline, Intersect.OnBothOperands, intersectWithResult, IntPtr.Zero, IntPtr.Zero);

                // 存储顶点
                HashSet vertices = new HashSet();
                int count = pPolyline.NumberOfVertices;
                for (int j = 0; j < count; j++)
                {
                    Autodesk.AutoCAD.Geometry.Point2d vertexd = pPolyline.GetPoint2dAt(j);
                    vertices.Add(new Point3d(vertexd.X, vertexd.Y, 0.0));
                }

                count = intersectWithResult.Count;
                for (int j = 0; j < intersectWithResult.Count; j++)
                {
                    Point3d tempPoint3D = intersectWithResult[j];
                    // 剔除顶点，获得真正的相交点
                    if (!vertices.Contains(tempPoint3D))
                    {
                        intersectPoint3Ds.Add(tempPoint3D);
                    }
                }


                return true;
            }
            catch (Exception ex)
            {
                error = ex;
                return false;
            }
        }

        #endregion