如何知道多义线Polyline（特别是封闭多义线）的时钟走向呢？从起点到终点是顺时针走向还是逆时针走向？

同时，本函数对于判断一个点位于封闭多义线内还是外也是有帮助的。

很抱歉：Lisp代码不是以一个完整函数的形式出现，懒得整理了

C#代码

    /// <summary>
    /// 判断轻型多义线的时钟走向
    /// Version : 2008.11.14
    /// </summary>
    /// <param name="pline">轻型多义性</param>
    /// <returns>顺时针返回-1,逆时针返回1</returns>
    static public int Clockwise(Polyline pline)
    {
      Polyline pline1 = (Polyline)pline.Clone();
      double bulge0 = pline1.GetBulgeAt(0);
      double area0 = pline1.Area;
      if (bulge0 == 0.0)
      {
        pline1.SetBulgeAt(0, 0.5);
        double area1 = pline1.Area;
        if (area1 > area0)
          return 1;
        else
          return -1;
      }
      else
      {
        pline1.SetBulgeAt(0, 0);
        double area1 = pline1.Area;
        if (bulge0 > 0)
        {
          if (area1 > area0)
            return -1;
          else
            return 1;
        }
        else
        {
          if (area1 > area0)
            return 1;
          else
            return -1;
        }
      }
    }

Visual Lisp 代码

     (setq bulge0 (vla-getbulge obj1 0)
    area0  (vla-get-area obj1)
     )
     (setq p11 (vlax-curve-getpointatparam obj1 0.5)
    p13 (vlax-curve-getpointatparam obj1 0)
    p14 (vlax-curve-getpointatparam obj1 1)
     )
     (if (= bulge0 0.0)
       (progn
  (vla-setbulge obj1 0 0.5)
  (setq area1 (vla-get-area obj1))
  (if (> area1 area0)
    (setq cxk_clocksize 1)
    (setq cxk_clocksize -1)
  )
       )
       (progn
  (vla-setbulge obj1 0 0.0)
  (setq area1 (vla-get-area obj1))
  (if (> area1 area0)
    (if (> bulge0 0)
      (setq cxk_clocksize -1)
      (setq cxk_clocksize 1)
    )
    (if (> bulge0 0)
      (setq cxk_clocksize 1)
      (setq cxk_clocksize -1)
    )
  )
       )
     )
     (vla-setbulge obj1 0 bulge0)

草木世交.Sieben