# OpenCascade Modeling Algorithms Fillets and Chamfers

## 造型算法——倒圆与倒角

eryar@163.com

### 一、倒圆FilletConstructor

#### 1． BRepFilletAPI_MakeFillet

l 首先，给定一个需要倒圆的形状；

l 最后，通过询问结果来执行倒圆操作。

Figure 1. Filleting two edges using radius r1 and r2

Figure 2. Filleting a box

a = 100b = 60c = 80r = 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())
{
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 4. Evolutive radius fillet a box

```  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

```  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ChamferConstructor

#### 1．BRepFilletAPI_MakeChamfer

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

Figure 5. Creating a chamfer

Figure 6. The box with chamfers

```  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: `