opencascade中的几种类型转换 [转自Polaris]

将Geom_BSplineSurface转化成TopoDS_Face：  

1. 将Geom_BSplineSurface转化成TopoDS_Face：

Handle_Geom_BSplineSurface BSurface;

BRep_Builder builder;
TopoDS_Face Face;
builder.MakeFace(Face,BSurface,Tolerance);

2.将TopoDS_Face 转化为Geom_Surface

Handle_Geom_Surface  currentSur;
TopExp_Explorer Ex; 
Ex.Init(shape,TopAbs_FACE); 
TopoDS_Face currentVt = TopoDS::Face(Ex.Current());
currentSur = BRep_Tool::Surface(currentVt);

3.普通曲线转化为NURBS曲线

Handle(Geom_Curve) ResCurve ;
Handle(Geom_TrimmedCurve) myTrimmed = new Geom_TrimmedCurve(ResCurve, 0, 1);
NurbsCurve = GeomConvert::CurveToBSplineCurve(myTrimmed); //必须指定曲线的类型如Geom_TrimmedCurve

OCC的说明如下：

 

-- Purpose : This function converts a non infinite curve from

-- Geom into a B-spline curve.C must be an ellipse or a

-- circle or a trimmed conic or a trimmed line or a Bezier

-- curve or a trimmed Bezier curve or a BSpline curve or a

-- trimmed BSpline curve or an OffsetCurve. The returned B-spline is

-- not periodic except if C is a Circle or an Ellipse.

 

4. Geom_Surface 转 Geom_BsplineSurface

GeomConvert::SurfaceToBSplineSurface(surface)

其中surface必须为Geom_Surface 中的某一具体类型

OCC的说明如下：

--- Purpose : This algorithm converts a non infinite surface from Geom

-- into a B-spline surface.

-- S must be a trimmed plane or a trimmed cylinder or a trimmed cone

-- or a trimmed sphere or a trimmed torus or a sphere or a torus or

-- a Bezier surface of a trimmed Bezier surface or a trimmed swept

--surfacewith a corresponding basis curve which can be turned into

-- a B-spline curve

5.  点云转 Geom_BsplineSurface

 

[cpp] view plain copy print ?

1. Handle_Geom_BSplineSurface CMiniCADTool::BuildSurface(const TColgp_SequenceOfXYZ& seqOfXYZ)  
2. {  
3.     // Build the surface:  
4.     // points are projected on plane z = 0  
5.     // the projection vector for each point is computed   
6.     // These data give the input constraints loaded into plate algorithm  
7.   
8.     const Standard_Integer nbPnt = seqOfXYZ.Length();  
9.     Standard_Integer i;  
10.   
11.     //Filling plate  
12.     Plate_Plate myPlate;  
13.     for (i=1; i<= nbPnt; i += 4) {  
14.         gp_Vec aVec(0., 0., seqOfXYZ.Value(i).Z());  
15.         gp_XY  pntXY(seqOfXYZ.Value(i).X(),seqOfXYZ.Value(i).Y());  
16.         Plate_PinpointConstraint PCst( pntXY,aVec.XYZ() );  
17.         myPlate.Load(PCst); // Load a pinpoint constraint  
18.     }  
19.     myPlate.SolveTI(2, 1.); // Solving plate equations  
20.     if (!myPlate.IsDone()) {  
21.         return Handle(Geom_BSplineSurface)();  
22.     }  
23.   
24.     // Computation of plate surface  
25.     gp_Pnt Or(0,0,0.);  
26.     gp_Dir Norm(0., 0., 1.);  
27.     Handle(Geom_Plane) myPlane = new Geom_Plane(Or, Norm);// Plane of normal Oz  
28.     Handle(GeomPlate_Surface) myPlateSurf = new GeomPlate_Surface(myPlane, myPlate);//plate surface  
29.   
30.     GeomPlate_MakeApprox aMKS(myPlateSurf, Precision::Approximation(), 4, 7, 0.001, 0);//bspline surface  
31.     return aMKS.Surface();  
32.   
33. }  

Handle_Geom_BSplineSurface CMiniCADTool::BuildSurface(const TColgp_SequenceOfXYZ& seqOfXYZ)
{
	// Build the surface:
	// points are projected on plane z = 0
	// the projection vector for each point is computed 
	// These data give the input constraints loaded into plate algorithm

	const Standard_Integer nbPnt = seqOfXYZ.Length();
	Standard_Integer i;

	//Filling plate
	Plate_Plate myPlate;
	for (i=1; i<= nbPnt; i += 4) {
		gp_Vec aVec(0., 0., seqOfXYZ.Value(i).Z());
		gp_XY  pntXY(seqOfXYZ.Value(i).X(),seqOfXYZ.Value(i).Y());
		Plate_PinpointConstraint PCst( pntXY,aVec.XYZ() );
		myPlate.Load(PCst); // Load a pinpoint constraint
	}
	myPlate.SolveTI(2, 1.); // Solving plate equations
	if (!myPlate.IsDone()) {
		return Handle(Geom_BSplineSurface)();
	}

	// Computation of plate surface
	gp_Pnt Or(0,0,0.);
	gp_Dir Norm(0., 0., 1.);
	Handle(Geom_Plane) myPlane = new Geom_Plane(Or, Norm);// Plane of normal Oz
	Handle(GeomPlate_Surface) myPlateSurf = new GeomPlate_Surface(myPlane, myPlate);//plate surface

	GeomPlate_MakeApprox aMKS(myPlateSurf, Precision::Approximation(), 4, 7, 0.001, 0);//bspline surface
	return aMKS.Surface();

}

6.surface 向Geom_Plane 向下转换（DownCast方法）其中Geom_Plane类中有方法可以将gp_Pln和Geom_Plane进行相互转化。

 Handle(Geom_Plane) aPlane = Handle(Geom_Plane)::DownCast(BRep_Tool::Surface(SelectFace));
PlaneOfTheView = aPlane->Pln();

 7.TopoDS_Shape 向相应的格式转

例如：Vertex = TopoDS::Vertex(Shape);

8.TopoDS_Vertex向gp_Pnt转

gp_Pnt   P = BRep_Tool::Pnt(Vertex)