造型算法——倒圓與倒角
Modeling Algorithms Fillets and Chamfers
eryar@163.com
一、倒圓Fillet Constructor
1． BRepFilletAPI_MakeFillet
使用類BRepFilletAPI_MakeFillet來為形狀添加倒圓。倒圓是用光滑面來代替角邊。使用方法如下：
l 首先，給定一個需要倒圓的形狀；
l 然后，通過Add方法來添加描述倒圓的參數(shù)，倒圓所需的參數(shù)包括一個邊edge和半徑radius。當然，邊edge必須由兩個面face所共有。倒圓會將原來的邊替換成光滑的圓面過渡。
l 最后，通過詢問結果來執(zhí)行倒圓操作。
注：添加一個倒圓兩次并不會出錯，因為只保留了最后一次添的倒圓。
Figure 1. Filleting two edges using radius r1 and r2
下面給出一個將創(chuàng)建一個倒圓的長方體，其尺寸分別為a，b，c，倒圓半徑r。
Figure 2. Filleting a box
代碼如下所示，創(chuàng)建上圖所示的倒圓的長方體的參數(shù)分別為：
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();
}
如下圖所示為創(chuàng)建一個半徑變化的倒圓操作：
Figure 3. Evolutive radius fillet
Figure 4. Evolutive radius fillet a box
程序代碼如下所示：
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.
我按照示例代碼運行了一下程序，結果程序總是崩潰，其操作的效果不得而知，所以也得不到真實的效果圖。將其程序代碼列出如下所示：
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
類BREpFilletAPI_MakeChamfer的使用方法與BRepFilletAPI_MakeFillet大致類似，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
程序代碼如下所示：
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: