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Volume mesh for a simple cylinder fails

Dflyer
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3 years 9 months ago #2976 by Dflyer

Volume mesh for a simple cylinder fails was created by Dflyer

A simple solid cylinder attached fails for volume mesh.

Last output lines

Surface meshing done
0 illegal triangles
WARNING! NOT ALL FACES HAVE BEEN MESHED
SURFACE MESHING ERROR OCCURRED IN 1 FACES:
Face 1

for more information open IGES/STEP Topology Explorer
Problem in Surface mesh generation

Attachments:

cylinder.step

Fried
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3 years 9 months ago #2984 by Fried

Replied by Fried on topic Volume mesh for a simple cylinder fails

+1 I get the same issue

christopher
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3 years 9 months ago #2987 by christopher

Replied by christopher on topic Volume mesh for a simple cylinder fails

The step file seems to not consist of one solid, but multiple free shells (that are not "glued" together). You can fix this with Geometry-> IGES/STEP Topology Explorer/Doctor and then Click the "Heal Geometry" button. Netgen then glues the geometry together and is able to mesh it.

Best
Christopher

Dflyer
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3 years 9 months ago #2993 by Dflyer

Replied by Dflyer on topic Volume mesh for a simple cylinder fails

Thanks Christopher, that worked,

I am meshing with C++ API.

The model attached fails in surface mesh, It mesh good in GUI, I am missing Analyze Geometry in C++, how can we do that in C++?

I could even reproduce the crash in surface mesh creation if I don't analyze geometry in GUI.

Thanks

Attachments:

2_2_1.stp

christopher
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3 years 9 months ago #2994 by christopher

Replied by christopher on topic Volume mesh for a simple cylinder fails

OCCGeometry has a Analyse function that should be called for this.
Actually if you call the GenerateMesh from the base class NetgenGeometry all function should be called in correct order and so. Probably thats what you want to do.
Best
Christopher

Dflyer
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3 years 9 months ago #3010 by Dflyer

Replied by Dflyer on topic Volume mesh for a simple cylinder fails

I tried to call the GenerateMesh from nglib.cpp like this

Code:

DLL_HEADER Ng_Result Ng_GenerateMesh( Ng_OCC_Geometry * geom,
	   Ng_Mesh * mesh,
	   Ng_Meshing_Parameters* mp )
   {
	   OCCGeometry * occgeom = (OCCGeometry*)geom;
	   std::shared_ptr< NetgenGeometry> netgenGeometry = shared_ptr<NetgenGeometry>( occgeom, &NOOP_Deleter );

	   shared_ptr<Mesh> netgenMesh( (Mesh*)mesh, &NOOP_Deleter );

	   netgenMesh->SetGeometry( netgenGeometry );
	   netgenMesh->geomtype = Mesh::GEOM_OCC;

	   mp->Transfer_Parameters();
	   mparam.perfstepsstart = MESHCONST_ANALYSE;
	   mparam.perfstepsend = MESHCONST_OPTSURFACE;

	   int res = netgenGeometry->GenerateMesh( netgenMesh, mparam );

	   if(res == 0 )
		   return( NG_OK );
   }

But it crashes at OCCMeshSurface

Code:

Meshing2OCCSurfaces meshing(geom, TopoDS::Face(geom.fmap(k)), bb, projecttype, mparam);

the value of k is greater than number of faces in the geometry (

File Attachment:

File Name: 2_2_1_2020-07-25.stp
File Size:11 KB

)
So it throws out of range error.

Thanks

Attachments:

2_2_1_2020-07-25.stp

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