CGAL users discussion list

[Sebastien Loriot <>]

Hello Adam,

did you already have a look at 
CGAL/Tetrahedral_remeshing/internal/flip_edges.h

flip_n_to_m() seems to be what you are looking for.

Jane is not around for a few weeks. I'm sure she will get back to
you when she's back.

Best,

Sebastien.

On 6/29/22 22:52, Adam Getchell ( via 
cgal-discuss Mailing List) wrote:
> Hello all,
>
> I’m working on a bistellar flip for 3D triangulations, briefly as follows:
>
> Step 1: Find a candidate edge for which a circulator around that edge 
> obtains 4 incident cells.
>
> Step 2: Get the 2 vertices comprising the candidate edge.
>
> Step 3: Get the remaining 4 vertices in the 4-cell complex (there are 6 
> vertices in the cell complex).
>
> Step 4: Obtain a new pivot edge between 2 different vertices for which a 
> circulator around that pivot edge would obtain 4 new incident cells 
> comprised of the 6 vertices.
>
> Step 5: Find the 8 neighboring cells of the original 4-cell complex.
>
> Step 6: Delete the old cells.
>
> Step 7: Create the new cells using the same 6 vertices.
>
> Step 8: Assign the 8 neighboring cells to the cells in the new 4-cell 
> complex.
>
> Details here: https://github.com/acgetchell/bistellar-flip 
> <https://github.com/acgetchell/bistellar-flip>
>
> The issue is at the conclusion of Step 8, all cells have been verified 
> as valid, cell orientations have been verified/reoriented, but the 
> triangulation itself is not valid.
>
> The error is: “neighbor of c has not c as neighbor”
>
> My question is, do I also need to track the 32 neighboring cells of the 
> 8 neighbors of the 4-cell complex being flipped? (And in my test case, 
> the 8 neighbors are all infinite.)
>
> Is there some other mistake?
>
> Thanks for your advice,
> Adam
>
> P.S. I have looked at the Tetrahedral Remeshing package at Sebastien 
> Loriot’s suggestion. I’m presently unsure if any of those functions 
> (e.g. construct_opposite_vector_3_object()) are relevant.
> --
> Adam Getchell
> https://adamgetchell.org <https://adamgetchell.org>
>
>
>
>
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