多义线凸度的计算

// houlinbo QQ420021327

                double A = Math.PI;
                double dBulge = Math.Sin(A / 4) / Math.Cos(A / 4);
                Polyline plCir = new Polyline();
                plCir.AddVertexAt(0, new Point2d(pt1.X - R / 2, pt1.Y), dBulge, R, R);
                plCir.AddVertexAt(1, new Point2d(pt1.X + R / 2, pt1.Y), dBulge, R, R);
                plCir.AddVertexAt(2, new Point2d(pt1.X - R / 2, pt1.Y), dBulge, R, R);

// houlinbo QQ420021327