目录

1、球面的Brep数据

2、C++遍历球面的边

---

​这里以球面为例来说明如何遍历曲面的边。

1、球面的Brep数据

使用Tcl命令在Draw Test Harness中生成的球面并到出Brep数据如下：

pload ALL

psphere asphere 1

dump asphere

结果如下：

*********** Dump of asphere *************

Shape : 9, FORWARD

Dump of 9 TShapes

-----------------

Flags : Free, Modified, Checked, Orientable, Closed, Infinite, Convex, Locked

TShape # 1 : SOLID     11000000 0000018AE4364B70

    +2

TShape # 2 : SHELL     01011000 0000018AE43648F0

    +3

TShape # 3 : FACE      01110000 0000018AE420C530

    +4

    Tolerance : 1e-07

    - Surface : 1

TShape # 4 : WIRE      01011000 0000018AE4364270

    -8 +6 +5 -6

TShape # 5 : EDGE      01010000 0000018AE3048880

    +7 -7

    Tolerance : 1e-07

     same parametrisation of curves

     same range on curves

     degenerated

    - PCurve : 4 on surface 1, range : 0 6.28318530717959

  UV Points : 0, -1.5707963267949 6.28318530717959, -1.5707963267949

TShape # 6 : EDGE      01010000 0000018AE3049CC0

    -9 +7

    Tolerance : 1e-07

     same parametrisation of curves

     same range on curves

    - Curve 3D : 1, range : 4.71238898038469 7.85398163397448

    - PCurve : 2, 3 (CN) on surface 1, range : 4.71238898038469 7.85398163397448

  UV Points : 6.28318530717959, -1.5707963267949 6.28318530717959, 1.5707963267949

  UV Points : 0, -1.5707963267949 0, 1.5707963267949

TShape # 7 : VERTEX    01011010 0000018AE420C6D0

    Tolerance : 1e-07

    - Point 3D : 6.12323399573677e-17, -1.49975978266186e-32, -1

TShape # 8 : EDGE      01010000 0000018AE3049C00

    +9 -9

    Tolerance : 1e-07

     same parametrisation of curves

     same range on curves

     degenerated

    - PCurve : 1 on surface 1, range : 0 6.28318530717959

  UV Points : 0, 1.5707963267949 6.28318530717959, 1.5707963267949

TShape # 9 : VERTEX    01011010 0000018AE420C600

    Tolerance : 1e-07

    - Point 3D : 6.12323399573677e-17, -1.49975978266186e-32, 1

 -------

Dump of 4 Curve2ds

 -------

   1 : Line

  Origin :0, 1.5707963267949

  Axis   :1, 0

   2 : Line

  Origin :6.28318530717959, -6.28318530717959

  Axis   :0, 1

   3 : Line

  Origin :0, -6.28318530717959

  Axis   :0, 1

   4 : Line

  Origin :0, -1.5707963267949

  Axis   :1, 0

 -------

Dump of 1 Curves

 -------

   1 : Circle

  Center :0, 0, 0

  Axis   :-2.44929359829471e-16, -1, 0

  XAxis  :1, -2.44929359829471e-16, 0

  YAxis  :0, 0, 1

  Radius :1

 -------

Dump of 0 Polygon3Ds

 -------

 -------

Dump of 0 PolygonOnTriangulations

 -------

 -------

Dump of 1 surfaces

 -------

   1 : SphericalSurface

  Center :0, 0, 0

  Axis   :0, 0, 1

  XAxis  :1, 0, -0

  YAxis  :-0, 1, 0

  Radius :1

 -------

Dump of 0 Triangulations

 -------

 -------

 Dump of 0 Locations

 -------

可见，球面的数据中有3条边

2、C++遍历球面的边

下面通过C++来读取所有边的参数范围，并判断边是否退化为点。

// OpenCascade library.
#define WNT
#include <TopoDS.hxx>
#include <TopExp.hxx>
#include <TopExp_Explorer.hxx>
#include <BRepPrimAPI_MakeSphere.hxx>
​
#include <TopTools_ListIteratorOfListOfShape.hxx>
#include <TopTools_IndexedDataMapOfShapeListOfShape.hxx>
​
#pragma comment(lib, "TKernel.lib")
#pragma comment(lib, "TKMath.lib")
#pragma comment(lib, "TKBRep.lib")
#pragma comment(lib, "TKTopAlgo.lib")
#pragma comment(lib, "TKPrim.lib")
​
/**
* @breif Find the face for the given edge, i.e the face which the given edge is on it.
*/
TopoDS_Face FindFaceOfEdge(const TopoDS_Shape& theShape, const TopoDS_Edge& theEdge)
{TopoDS_Face theFace;
​TopTools_IndexedDataMapOfShapeListOfShape theMap;TopExp::MapShapesAndAncestors(theShape, TopAbs_EDGE, TopAbs_FACE, theMap);
​const TopTools_ListOfShape& theFaces = theMap.FindFromKey(theEdge);TopTools_ListIteratorOfListOfShape theIterator(theFaces);
​for (theIterator.Initialize(theFaces); theIterator.More(); theIterator.Next()){theFace = TopoDS::Face(theIterator.Value());}
​return theFace;
}
​
void TestSingularity(void)
{TopoDS_Shape theSphere = BRepPrimAPI_MakeSphere(1.0);
​for (TopExp_Explorer edgeExp(theSphere, TopAbs_EDGE); edgeExp.More(); edgeExp.Next()){const TopoDS_Edge anEdge = TopoDS::Edge(edgeExp.Current());
​Standard_Real aFirst = 0.0;Standard_Real aLast = 0.0;
​gp_Pnt2d U1V1;gp_Pnt2d U2V2;
​Standard_Boolean IsDegenerated = BRep_Tool::Degenerated(anEdge);
​BRep_Tool::Range(anEdge, aFirst, aLast);BRep_Tool::UVPoints(anEdge, FindFaceOfEdge(theSphere, anEdge), U1V1, U2V2);
​std::cout << "Edge is Degenerated: " << (IsDegenerated ? "True" : "False") << std::endl;std::cout << "Edge parameters on face: " << std::endl;std::cout << "  (" << U1V1.X() << ", " << U1V1.Y() << ")" << std::endl;std::cout << "  (" << U2V2.X() << ", " << U2V2.Y() << ")" << std::endl;std::cout << std::endl;}
}
​
int main(int argc, char* argv[])
{TestSingularity();
​return 0;
}

Edge is Degenerated: True

Edge parameters on face:

  (0, 1.5708)

  (6.28319, 1.5708)

Edge is Degenerated: False

Edge parameters on face:

  (6.28319, -1.5708)

  (6.28319, 1.5708)

Edge is Degenerated: True

Edge parameters on face:

  (0, -1.5708)

  (6.28319, -1.5708)

Edge is Degenerated: False

Edge parameters on face:

  (0, -1.5708)

  (0, 1.5708)