[petsc-users] DMPlex tetrahedra facets orientation

[Matthew Knepley]

On Mon, Feb 8, 2021 at 6:01 AM Nicolas Barral <
nicolas.barral at math.u-bordeaux.fr> wrote:

> Hi all,
>
> Can I make any assumption on the orientation of triangular facets in a
> tetrahedral plex ? I need the inward facet normals. Do I need to use
> DMPlexGetOrientedFace or can I rely on either the tet vertices ordering,
> or the faces ordering ? Could DMPlexGetRawFaces_Internal be enough ?
>

You can do it by hand, but you have to account for the face orientation
relative to the cell. That is what
DMPlexGetOrientedFace() does. I think it would be easier to use the
function below.


> Alternatively, is there a function that computes the normals - without
> bringing out the big guns ?
>

This will compute the normals

https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/DMPLEX/DMPlexComputeCellGeometryFVM.html

Should not be too heavy weight.

  THanks,

    Matt

Thanks
>
> --
> Nicolas
>


-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener

https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
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