AutoCAD C polyline small acute angle detection

 

        #region  Small acute angle detection 

        public static bool AcuteAngleDetect(Polyline pPolyline, double toloranceAngle, out List<Point3d> listPoint3Ds, out Exception error)
        {
            error = null;
            listPoint3Ds = new List<Point3d>();
            try
            {
                List<double> angles = new List<double>();
                int vertexNum = pPolyline.NumberOfVertices;
                Point3d pointFirst = new Point3d();
                Point3d pointSecond = new Point3d();
                //  Traverse to obtain the vertex coordinates of the polyline 
                for (int i = 0; i < vertexNum-1; i++)
                {
                    pointFirst = pPolyline.GetPoint3dAt(i);
                    pointSecond = pPolyline.GetPoint3dAt(i + 1);

                    double angle = GetAngleByTwoPoint(pointFirst, pointSecond);
                    if (i>0)
                    {
                        double preAngle = angles[i-1];
                        if (DetectAcuteAngleUsingVectorAngle(toloranceAngle, preAngle, angle))
                        {
                            listPoint3Ds.Add(pointFirst);
                        }
                    }
                    angles.Add(angle);
                }
                if (pPolyline.Closed)
                {
                    //  Calculate the penultimate angle 
                    pointFirst = pPolyline.GetPoint3dAt(vertexNum - 1);
                    pointSecond = pPolyline.GetPoint3dAt(0);
                    double angle = GetAngleByTwoPoint(pointFirst, pointSecond);
                    double preAngle = angles[angles.Count-1];
                    if (DetectAcuteAngleUsingVectorAngle(toloranceAngle, preAngle, angle))
                    {
                        listPoint3Ds.Add(pointFirst);
                    }

                    //  Calculate the last angle 
                    angle = angles[angles.Count - 1];
                    preAngle = angles[0];
                    if (DetectAcuteAngleUsingVectorAngle(toloranceAngle, preAngle, angle))
                    {
                        listPoint3Ds.Add(pPolyline.GetPoint3dAt(0));
                    }
                }


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

        public static double GetAngleByTwoPoint(Point3d first, Point3d second)
        {
            return Math.Atan2(second.Y - first.Y, second.X - first.X) * 180 / Math.PI;
        }

        public static bool DetectAcuteAngleUsingVectorAngle(double toloranceAngle, double angleFirst, double angleSecond)
        {
            return Math.Abs(Math.Abs(angleSecond - angleFirst) - 180) < toloranceAngle;
        }

        #endregion