[MOAB-dev] Boundary nodes and faces

[Vijay S. Mahadevan]

Tim, Iulian,

Thanks for the pointers. I think going from the highest-dimension down and
removing shared entities from the list makes sense. I have a partial
implementation that already does this and will check whether this algorithm
yields what I need.

I was originally thinking that Skinner:: find_geometric_skin would give me
the boundary vertices but doing it by the process of elimination might be
the right way since there is no reliance on GEOM_DIMENSION tag being
explicitly defined.

Shall update soon.
Vijay


On Wed, Aug 14, 2013 at 9:50 PM, Tim Tautges <tautges at mcs.anl.gov> wrote:

> Note, I've added this to the MOAB faq, http://trac.mcs.anl.gov/**
> projects/ITAPS/wiki/**ParallelGeomSkin<http://trac.mcs.anl.gov/projects/ITAPS/wiki/ParallelGeomSkin>
> .
>
> - tim
>
>
> On 08/14/2013 09:31 PM, Tim Tautges wrote:
>
>> This is tricky.  As you say, if you get the local skin, that'll include
>> interior entities shared with/ghosted from other
>> procs.  If you get the skin and remove the shared entities, that'll
>> remove the vertices that are on the geometric skin
>> but also shared with other procs.  The right way to do this is:
>>
>> - get the highest-dimensional entities on the skin (1d if in 2d, 2d if in
>> 3d)
>> - remove any shared entities from that range (because if it's shared,
>> then by definition there will be d+1 - dimensional
>> entities on the other proc)
>> - if you're in 3d and you also want skin edges, get the edges adj to the
>> entities in the range (remember the UNION arg
>> on get_adjacencies), put in tmp range, then do the same for vertices,
>> also put in tmp range
>> - merge the tmp range with the original range
>>
>> Like I said, tricky, but welcome to parallel mesh.
>>
>
> --
> ==============================**==============================**====
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>   steadfast, because he trusts in you."               Isaiah 26:3
>
>              Tim Tautges            Argonne National Laboratory
>          (tautges at mcs.anl.gov)      (telecommuting from UW-Madison)
>  phone (gvoice): (608) 354-1459      1500 Engineering Dr.
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