Problem when trying to convert an Edge to a Geom_Curve

Kreshnik's picture
Kreshnik
Fri, 05/20/2005 - 14:40
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Other usage issues

Hi,

I need to convert an Edge to a Geom_Curve. I did that and there are not compilation error :

Handle(Geom_Curve) myCurve = BRep_Tool::Curve(myEdge, First, Last);
Handle(Geom_BSplineCurve) myBSplCurve = Handle(Geom_BSplineCurve)::DownCast( myCurve);

Standard_Integer ival = myBSplCurve->NbPoles();

When I execute the program I have an error on this last line.
Error at adress ... Memory cannot be "read".

Can someone help me.

Thanks in advance,

Rob Bachrach's picture
Rob Bachrach
Fri, 05/20/2005 - 14:46

Are you sure your edge is based on a BSplineCurve? It is very possible that your DownCast is returning an invalid pointer (indicating an invalid cast). If you need it to be a BSpline, you
may want to look at the GeomConvert package.

Kreshnik's picture
Kreshnik
Fri, 05/20/2005 - 15:07

Hi Rob,

Thanks for your quick answer. My edge is an edge of a cube that I've selected. In reality it's a segment. I cannot convert a segment in a BSplineCurve ???
I havn't this problem when I convert the cube face in a BSplineSurface !

Thanks for your answer.

Roman Lygin's picture
Roman Lygin
Fri, 05/20/2005 - 19:21

Use GeomConvert::CurveToBSplineCurve() to convert your line to BSpline first. Another method could be ShapeConvert::ConvertCurveToBSpline(). It offers more parameters (user-defined tolerance, max/min degree) and first tries to reapproximate with those parameters, and then calls GeomConvert if not successful. See the source code for details.

Roman