opencascade中的几种类型转换(点云转nurbs曲面）

原文链接： https://blog.csdn.net/shlkl99/article/details/8175206

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

–surface with a corresponding basis curve which can be turned into

– a B-spline curve

5. 点云转 Geom_BsplineSurface

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();

}