OpenCascade Modeling Algorithms Fillets and Chamfers

Modeling Algorithms Fillets and Chamfers

造型算法——倒圆与倒角

eryar@163.com

一、倒圆Fillet Constructor

1． BRepFilletAPI_MakeFillet

使用类BRepFilletAPI_MakeFillet来为形状添加倒圆。倒圆是用光滑面来代替角边。使用方法如下： 

l 首先，给定一个需要倒圆的形状； 

l 然后，通过Add方法来添加描述倒圆的参数，倒圆所需的参数包括一个边edge和半径radius。当然，边edge必须由两个面face所共有。倒圆会将原来的边替换成光滑的圆面过渡。 

l 最后，通过询问结果来执行倒圆操作。 

注：添加一个倒圆两次并不会出错，因为只保留了最后一次添的倒圆。

Figure 1. Filleting two edges using radius r1 and r2

下面给出一个将创建一个倒圆的长方体，其尺寸分别为a，b，c，倒圆半径r。 

Figure 2. Filleting a box

代码如下所示，创建上图所示的倒圆的长方体的参数分别为： 

a = 100，b = 60，c = 80，r = 10：

#include <TopoDS_Shape.hxx> 
#include <TopoDS.hxx> 
#include <BRepPrimAPI_MakeBox.hxx> 
#include <TopoDS_Solid.hxx> 
#include <BRepFilletAPI_MakeFillet.hxx> 
#include <TopExp_Explorer.hxx> 

TopoDS_Shape FilletedBox(const Standard_Real a, 
      const Standard_Real b, 
      const Standard_Real c, 
      const Standard_Real r) 
{ 
    TopoDS_Solid Box = BRepPrimAPI_MakeBox(a,b,c); 
    BRepFilletAPI_MakeFillet MF(Box); 

    // add all the edges to fillet 
    TopExp_Explorer ex(Box,TopAbs_EDGE); 

    while (ex.More()) 
    { 
        MF.Add(r,TopoDS::Edge(ex.Current())); 
        ex.Next(); 
    }
    return MF.Shape(); 
} 

 如下图所示为创建一个半径变化的倒圆操作： 

Figure 3. Evolutive radius fillet

Figure 4. Evolutive radius fillet a box

程序代码如下所示：

  1:     TopoDS_Shape theBox = BRepPrimAPI_MakeBox(200, 200, 200);

  2:     BRepFilletAPI_MakeFillet Rake(theBox);

  3:     ChFi3d_FilletShape FSH = ChFi3d_Rational;

  4:     Rake.SetFilletShape(FSH);

  5:  

  6:     TColgp_Array1OfPnt2d parAndRad(1, 6);

  7:     parAndRad.SetValue(1, gp_Pnt2d(0, 10));

  8:     parAndRad.SetValue(2, gp_Pnt2d(50, 20));

  9:     parAndRad.SetValue(3, gp_Pnt2d(70, 20));

 10:     parAndRad.SetValue(4, gp_Pnt2d(130, 60));

 11:     parAndRad.SetValue(5, gp_Pnt2d(160, 30));

 12:     parAndRad.SetValue(6, gp_Pnt2d(200, 20));

 13:  

 14:     TopExp_Explorer ex(theBox, TopAbs_EDGE);

 15:     Rake.Add(parAndRad, TopoDS::Edge(ex.Current()));

 16:     TopoDS_Shape evolvedBox = Rake.Shape();

 17: 

2． BRepFilletAPI_MakeFillet2d

BRepFilletAPI_MakeFillet2d is used to construct fillets and chamfers on planar faces. 

我按照示例代码运行了一下程序，结果程序总是崩溃，其操作的效果不得而知，所以也得不到真实的效果图。将其程序代码列出如下所示：

  1: #include “BRepPrimAPI_MakeBox.hxx” 

  2: #include “TopoDS_Shape.hxx” 

  3: #include “TopExp_Explorer.hxx” 

  4: #include “BRepFilletAPI_MakeFillet2d.hxx” 

  5: #include “TopoDS.hxx” 

  6: #include “TopoDS_Solid.hxx” 

  7:  

  8: TopoDS_Shape FilletFace(const Standard_Real a, 

  9:     const Standard_Real b, 

 10:     const Standard_Real c, 

 11:     const Standard_Real r) 

 12: { 

 13:     TopoDS_Solid Box = BRepPrimAPI_MakeBox (a,b,c); 

 14:     TopExp_Explorer ex1(Box,TopAbs_FACE); 

 15:  

 16:     const TopoDS_Face& F = TopoDS::Face(ex1.Current()); 

 17:     BRepFilletAPI_MakeFillet2d MF(F); 

 18:     TopExp_Explorer ex2(F, TopAbs_VERTEX); 

 19:  

 20:     while (ex2.More()) 

 21:     { 

 22:         MF.AddFillet(TopoDS::Vertex(ex2.Current()),r); 

 23:         ex2.Next(); 

 24:     } 

 25:  

 26:     // while... 

 27:     return MF.Shape(); 

 28: }

 29: 

二、倒角Chamfer Constructor

1．BRepFilletAPI_MakeChamfer

类BREpFilletAPI_MakeChamfer的使用方法与BRepFilletAPI_MakeFillet大致类似，但稍有不同： 

a) The surfaces created are ruled and not smooth; 

b) The Add syntax for selecting edges requires one or two distances, one edge and one face(contiguous to the edge); 

Add(dist, E, F); 

Add(d1, d2, E, F); with d1 on the face F. 

Figure 5. Creating a chamfer

Figure 6. The box with chamfers

程序代码如下所示：

  1: TopoDS_Shape theBox = BRepPrimAPI_MakeBox(130,200,170); 

  2: BRepFilletAPI_MakeChamfer MC(theBox); 

  3: TopTools_IndexedDataMapOfShapeListOfShape M; 

  4: TopExp::MapShapesAndAncestors(theBox,TopAbs_EDGE,TopAbs_FACE,M); 

  5:  

  6: for (Standar1d_Integer i;i<M.Extent();i++) 

  7: { 

  8:     TopoDS_Edge E = TopoDS::Edge(M.FindKey(i)); 

  9:     TopoDS_Face F = TopoDS::Face(M.FindFromIndex(i).First()); 

 10:     MC.Add(15,15,E,F); 

 11: } 

 12:  

 13: TopoDS_Shape ChanfrenedBox = MC.Shape();  

 14: