Tue, 06/15/2004 - 13:14
Forums:
Hi,
I am trying to do a projection of a TopoDS_Wire on a TopoDS_Face.
So far I tried to use BrepOffsetAPI_NormalProjection, but it seems to work only on 2D surfaces.
Now if I want to use GeomProjLib::Project, how can I convert the wire in a Geom_Curve and the face in Geom_Surface?
Or is there any better way of calculating the projection? In result I am looking for a wire that is conformal to the surface and can be evolved.
Regards,
Udo
Tue, 06/15/2004 - 14:07
Use class BRep_Tool and its static functions to translate topology entities to geometric entities.
There are functions "Curve" and "Surface".
To translate a TopoDS_Wire, I think you will need to iterate on the edges of that wire and translate them to Geom_Curve objects.
Use class TopExp_Explorer to iterate on a topology entity.
Thu, 06/17/2004 - 17:05
Thanks a lot, like most of the time it is easy if you know the right class. I am learned a lot of the API until now. But still there are a lot of questions...
Thu, 06/17/2004 - 18:10
As for now I am able to do the projection using: Handle(Geom_Curve) projection = GeomProjLib::Project(aCurve, aSurface);. But actually I just want the part of the edge that is in the range of the face that I am currently looking at. Now it is just doing the projection to the plane the face is lying in. I guess Curve2d is doing such a thing but I would not expect a 2D curve as the result? What point am I missing here?
Regards,
Udo
Mon, 06/21/2004 - 17:05
Hi,
I have never tried to project a curve on a surface with OCC. I have just taken a look at the implementation file of GeomProjLib(look at src/GeomProjLib/GeomProjLib.cxx).
Static function "GeomProjLib::Project" makes use of class "ProjLib_CompProjectedCurve".
You should consider and test this class, see its interface(the CDL file), particularly routines "FirstParameter" and "LastParameter". They seem to give what you want.
Mon, 06/21/2004 - 18:57
Thank you, it seems to be necessary to go through the implementation of commands from time to time. I found that my face is handled by the
if ( AS.GetType() == GeomAbs_Plane) {
ProjLib_ProjectOnPlane Proj( AS.Plane().Position());
[...]
part of GeomProjLib::Project.
This would explain the result of receiving a projection on planes. However, I do not understand why I receive a GeomAbs_Plane instance when I call:
Handle(Geom_Surface) aSurface = BRep_Tool::Surface(aCurrentFace);
Here the sourcecode does not give any hints. Any suggestions?
Regards,
Udo
Mon, 06/21/2004 - 20:37
Are you working with a curve and a plane?
If so what is the problem then?
Tue, 06/22/2004 - 00:37
No, actually I am working with a TopoDS_Wire and a TopoDS_Face. I imported a STEP file and used a Face Explorer to apply the projection to every face with a normal with positiv z-component.
I then use Brep_Tool and a wire explorer to transform the wire to a Geom_Curve and Brep_Tool::Surface to transform the face into a surface.
Of course the face is lying in a plane, but I am only interested in the projection on that part of the the face wich is really forming my shell of the current AIS_Shape, i.e. the imported STEP file.