Wed, 05/28/2003 - 13:10
I use the followng code to get the 2D polygons on a certain Face
1.I get exception when calling Poly_Polygon2D::NbNodes
2. When I try to access points returned by
Poly_Polygon2D::Nodes
I get invalid values.
for (ExFace.Init(aShape, TopAbs_FACE); ExFace.More(); ExFace.Next())
{
// Reading edges
for (ExEdge.Init(ExFace.Current(),TopAbs_EDGE); ExEdge.More(); ExEdge.Next())
{
// Getting polygons of the current face on the current edge
TopoDS_Edge myEdge;
TopoDS_Face myFace;
myEdge = TopoDS::Edge(ExEdge.Current());
myFace = TopoDS::Face(ExFace.Current());
Handle(Poly_Polygon2D) my2DPolygon = BRep_Tool::PolygonOnSurface( myEdge,myFace );
if ( NULL == my2DPolygon )
continue;
Standard_Integer nNodes = my2DPolygon->NbNodes();
TColgp_Array1OfPnt2d arrayOf2DPoints(1,nNodes);
Standard_Integer nXVal = arrayOf2DPoints(1).X();
}// edges loop
}// faces loop
Wed, 05/28/2003 - 15:44
Hi,
You cannot test
if ( NULL == my2DPolygon )
use
if ( my2DPolygon.IsNull())
Because the Handle_* classes are smart pointers.
HTH
Wed, 05/28/2003 - 17:01
Ok thanks Stephane you are right, IsnNull() returned TRUE.
Now I also tried the following, I always get IsNull() equal to TURE, why is that?
for (ExFace.Init(aShape, TopAbs_FACE); ExFace.More(); ExFace.Next())
{
TopoDS_Face F = TopoDS::Face(ExFace.Current());
TopLoc_Location L;
Handle(Poly_Triangulation) myTriangulation = BRep_Tool::Triangulation(F, L);
if ( myTriangulation .IsNull())
continue;
Standard_Integer nNodes = myTriangulation->NbNodes();
}
Wed, 05/28/2003 - 17:25
Hello,
BRep_Tool::Triangulation does not build the triangulation, it just retrieve it from the Face.
By default TopoDS_Face have no triangulation. To build the triangulation you can use BRepMesh_IncrementalMesh
Regards.
Wed, 05/28/2003 - 17:31
I took a look at your link Stephane, I believe now that you have a full undersatanding of opencascade ins and outs. I hope you can help me in this:
I am currently developing an application to import IGES files, I already have an SDK for drawing elementary 3D vector objects:
POLYGON,POLYLINE,RECTANGLE,...
When I used "IGESControl_Reader" to read IGES files, I got shapes of type "TopoDS_Face". I didn't know how to deal with them, but some people here instructed me that I should convert them to surfaces.
When I took a look at the surfaces documentaion in OpenCASCADE, I couldn't understand much, and my vector SDK can't deal with surfaces.
My final goal is to be able to
-Convert any objects I get from OpenCASCADE into polylines,polygons,ellipses,..
OR
-Get the object in the form of 3D points to be able to generate them all as polygons
How can I do so?