[MOAB-dev] MOAB finding shells bounding closed regions in nonmanifold mesh

[Paul Wilson]

Hi Steve,

The GeomTopoTool assumes that a mesh-based geometry follows the data model conventions described in slides 1-6 of this summary<https://urldefense.us/v3/__https://docs.google.com/presentation/d/10m8e6GN8DhLpNHHSOMniZ2pDU9DOAiD0xJF1Zyewzh8/edit*slide=id.g3b5f37914c_0_117__;Iw!!G_uCfscf7eWS!aikrROa0FYIQY2AXg7JHjNZwoYJY6k57S-9wblXG0I_RwYsZDEk0fXfA3fS1Aa_JPgvT7TODKuh9CMkHNFXFKQ7jQJo$ >, and assumes that the relationships defined there are embedded when the mesh-based geometry is created.

I’m not sure I fully understand your question/use case, but you may also be interested in the MOAB skinner<https://ftp.mcs.anl.gov/pub/fathom/moab-docs/classmoab_1_1Skinner.html> that is designed to identify boundary elements.

I hope this is somewhat helpful,
Paul

--
-- ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ --
Paul P.H. Wilson (he/him/his)
Grainger Professor of Nuclear Engineering
Chair, Department of Nuclear Engineering & Engineering Physics
o: 608-263-0807, c: 608-469-9615
paul.wilson at wisc.edu<mailto:paul.wilson at wisc.edu>
153 Engineering Research Bldg
1500 Engineering Dr, Madison, WI 53706
Zoom Meeting Room: https://urldefense.us/v3/__https://uwmadison.zoom.us/j/6082630807__;!!G_uCfscf7eWS!aikrROa0FYIQY2AXg7JHjNZwoYJY6k57S-9wblXG0I_RwYsZDEk0fXfA3fS1Aa_JPgvT7TODKuh9CMkHNFXF2SVJZsU$ 
Zoom Phone Access: +1-929-205-6099, Access code: 6082630807
Computational Nuclear Engineering Research Group<https://urldefense.us/v3/__http://cnerg.engr.wisc.edu__;!!G_uCfscf7eWS!aikrROa0FYIQY2AXg7JHjNZwoYJY6k57S-9wblXG0I_RwYsZDEk0fXfA3fS1Aa_JPgvT7TODKuh9CMkHNFXFJpau_jQ$ >



From: moab-dev <moab-dev-bounces at mcs.anl.gov> on behalf of Steve Hughey <hugheyst at gmail.com>
Date: Wednesday, January 22, 2025 at 05:12
To: moab-dev at mcs.anl.gov <moab-dev at mcs.anl.gov>
Subject: [MOAB-dev] MOAB finding shells bounding closed regions in nonmanifold mesh
Hello,

I am using MOAB as the basis for a sort of mesh-based geometry model in a
finite element/boundary element code. I must assume that the mesh
connectivity and Exodus block specifications are the only information I
have about the geometry. I have been able to use MOAB’s various adjacency
queries to break the input mesh into connected components with adjacencies
between them, largely along the lines of CUBIT’s mesh-based geometry
engine. The meshes are pretty general, containing quads, tris, hexes, tets,
prisms, and pyramids, and typically contain nonmanifold edges.

However, I am now faced with the problem of finding closed regions. I have
some ideas on how to do this based on concepts from half-facet data
structures, but the MOAB classes FBEngine and GeomTopoTool caught my
attention. I have tried reading the interface specification for these and
have been unable to determine whether they could be useful for my closed
regions problem. I have seen many allusions in the code to geometry and
topology representation, but I haven’t been able to connect the dots. My
hope is that someone has already thought through this problem and
implemented a solution. I would appreciate any insight you can provide, and
in the meantime I will continue testing things.

Thanks,
Steve