/// <summary>
 /// 每一次创建管道的时候初始状态获取点的方式是从界面上选取一点
 /// 后面都是从上一次的尾点开始
 /// </summary>
 /// <returns>空或者尾点坐标,空意味着管道创建结束</returns>
 public Point3d? CreatePipeLineWithoutInitialPoint(out bool status)
 {
     status = false;
     PipeLine newPipeLine = null;
     PipeJig jig = new PipeJig(null);
     if (!jig.StartDraw(out status)) { return null; }
     newPipeLine = new PipeLine((Point3d)jig.startPoint, jig.endPoint, false, this);
     //相交测试
     //和简单接口测试相交
     return this.PipeLineCrossTest(newPipeLine);
 }
 /// <summary>
 /// 从一固定点创建管道
 /// </summary>
 /// <param name="startPoint"></param>
 /// <returns>返回结果如上</returns>
 public Point3d? CreatePipeLineConnectedPipeLine(Point3d startPoint, out bool status)
 {
     PipeLine newPipeline = null;
     PipeJig jig = new PipeJig(startPoint);
     if (!jig.StartDraw(out status)) { return null; }
     newPipeline = new PipeLine((Point3d)jig.startPoint, jig.endPoint, false, this);
     return this.PipeLineCrossTest(newPipeline);
 }