Open Cascade造型算法—

原文： Open Cascade造型算法——倒圆与倒角

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：

TopoDS_Shape theBox = BRepPrimAPI_MakeBox(200, 200, 200);
BRepFilletAPI_MakeFillet Rake(theBox);
ChFi3d_FilletShape FSH = ChFi3d_Rational;
Rake.SetFilletShape(FSH);

TColgp_Array1OfPnt2d parAndRad(1, 6);
parAndRad.SetValue(1, gp_Pnt2d(0, 10));
parAndRad.SetValue(2, gp_Pnt2d(50, 20));
parAndRad.SetValue(3, gp_Pnt2d(70, 20));
parAndRad.SetValue(4, gp_Pnt2d(130, 60));
parAndRad.SetValue(5, gp_Pnt2d(160, 30));
parAndRad.SetValue(6, gp_Pnt2d(200, 20));TopExp_Explorer ex(theBox, TopAbs_EDGE);
Rake.Add(parAndRad, TopoDS::Edge(ex.Current()));
TopoDS_Shape evolvedBox = Rake.Shape();

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：

PS：我想应该是TopExp_Explorer的问题吧，顶点构成边时共享使用了多次，改用TopExp::MapShapes(srcFace,TopAbs_VERTEX,mapVertex);即可。

#include “BRepPrimAPI_MakeBox.hxx”
#include “TopoDS_Shape.hxx”
#include “TopExp_Explorer.hxx”
#include “BRepFilletAPI_MakeFillet2d.hxx”
#include “TopoDS.hxx”
#include “TopoDS_Solid.hxx” TopoDS_Shape FilletFace(const Standard_Real a, const Standard_Real b, const Standard_Real c, const Standard_Real r) { TopoDS_Solid Box = BRepPrimAPI_MakeBox (a,b,c); TopExp_Explorer ex1(Box,TopAbs_FACE); const TopoDS_Face& F = TopoDS::Face(ex1.Current()); BRepFilletAPI_MakeFillet2d MF(F); TopExp_Explorer ex2(F, TopAbs_VERTEX); while (ex2.More()) { MF.AddFillet(TopoDS::Vertex(ex2.Current()),r); ex2.Next(); } // while... return MF.Shape(); }

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：

TopoDS_Shape theBox = BRepPrimAPI_MakeBox(130,200,170);
BRepFilletAPI_MakeChamfer MC(theBox);
TopTools_IndexedDataMapOfShapeListOfShape M;
TopExp::MapShapesAndAncestors(theBox,TopAbs_EDGE,TopAbs_FACE,M); for (Standar1d_Integer i;i<M.Extent();i++)
{ TopoDS_Edge E = TopoDS::Edge(M.FindKey(i)); TopoDS_Face F = TopoDS::Face(M.FindFromIndex(i).First()); MC.Add(15,15,E,F);
} TopoDS_Shape ChanfrenedBox = MC.Shape();