opencascade 小技巧截取两点间的曲线

输入：
曲线、曲线上两点
输出
曲线上两点间的曲线
代码：

  public bool Test(TopoDS_Shape aS, gp_Pnt ptF, gp_Pnt ptE, ref TopoDS_Shape resShape, double tol = 0.00000001)
  {
      if (aS.ShapeType() == TopAbs_ShapeEnum.TopAbs_EDGE || aS.ShapeType() == TopAbs_ShapeEnum.TopAbs_WIRE)
      {
          List<TopoDS_Shape> edges = new List<TopoDS_Shape>();
          TopExp_Explorer explor = new TopExp_Explorer(aS, TopAbs_ShapeEnum.TopAbs_EDGE);
          while (explor.More())
          {
              edges.Add(explor.Current());
              explor.Next();
          }
          BRepBuilderAPI_MakeVertex vertex = new BRepBuilderAPI_MakeVertex(ptF);
          TopoDS_Vertex vertedx = vertex.Vertex();
          BRepBuilderAPI_MakeWire makeWire = new BRepBuilderAPI_MakeWire();
          bool isCalf = false;
          foreach (var edge in edges)
          {
              BRepExtrema_DistShapeShape disshapshape = new BRepExtrema_DistShapeShape(edge, vertedx);
              if (!disshapshape.IsDone()) continue;
              if (disshapshape.Value() > tol) continue;
              TopoDS_Edge _edge = TopoDS.ToEdge(edge);

              double first = 0.0;
              double last = 0.0;
              Geom_Curve geom_Curve = BRep_Tool.Curve(_edge, ref first, ref last);
              bool CalEndPnt(ref TopoDS_Shape _resShape)
              {
                  if (_resShape == null) _resShape = new TopoDS_Shape();
                  var lPnt = geom_Curve.Value(last);
                  var __edge = new BRepBuilderAPI_MakeEdge(geom_Curve, ptF, ptE);
                  makeWire.Add(__edge.Edge());
                  makeWire.IsDone();
                  _resShape.shape = makeWire.Shape();
                  return true;
              }
              if (isCalf)
              {
                  var lPnt = geom_Curve.Value(last);
                  if (lPnt.Distance(ptE) < tol)
                  {
                      makeWire.Add(_edge);
                      if (resShape == null) resShape = new TopoDS_Shape();
                      makeWire.IsDone();
                      resShape.shape = makeWire.Shape();
                  }
                  else
                  {
                      var __edge = new BRepBuilderAPI_MakeEdge(geom_Curve, geom_Curve.Value(first), ptE);
                      makeWire.Add(__edge.Edge());
                      makeWire.IsDone();
                      if (resShape == null) resShape = new TopoDS_Shape();
                      resShape.shape = makeWire.Shape();
                  }
                  return true;
              }
              else
              {
                  var fPnt = geom_Curve.Value(first);
                  if (fPnt.Distance(ptF) < tol)
                  {
                      vertedx = (new BRepBuilderAPI_MakeVertex(ptE)).Vertex();
                      disshapshape = new BRepExtrema_DistShapeShape(edge, vertedx);
                      if (!disshapshape.IsDone() || disshapshape.Value() > tol)
                      {
                          makeWire.Add(_edge);
                          isCalf = true;
                          continue;
                      }
                      return CalEndPnt(ref resShape);
                  }
                  else
                  {
                      vertedx = (new BRepBuilderAPI_MakeVertex(ptE)).Vertex();
                      disshapshape = new BRepExtrema_DistShapeShape(edge, vertedx);
                      if (!disshapshape.IsDone() || disshapshape.Value() > tol)
                      {
                          var __edge = new BRepBuilderAPI_MakeEdge(geom_Curve, ptF, geom_Curve.Value(last));
                          makeWire.Add(__edge.Edge());
                          continue;
                      }
                      return CalEndPnt(ref resShape);
                  }
              }
          }
      }
      return false;
  }