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
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: