Open Cascade造型算法—

造型算法——倒圆与倒角

Modeling Algorithms Fillets and Chamfers

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