CGAL users discussion list

[Monique Teillaud <>]

Dear Matthew,

If I understand correctly (I am not sure) you would like to mesh multiple 
domains. 
Does this example help you?
https://doc.cgal.org/latest/Periodic_3_mesh_3/index.html#title19

Best,
--
Monique Teillaud 
https://members.loria.fr/Monique.Teillaud/
INRIA Nancy - Grand Est, LORIA 
Institut National de Recherche en Informatique et Automatique

----- Le 16 Mar 21, à 15:48, cgal-discuss  a écrit :

> Dear Monique,
> 
> I agree that adding points on the facets of the bounding cube in the
> right places would be a way to solve this. But this technique requires
> a description of the regions on each facet that should be
> triangulated. This is difficult because many of the surfaces I am
> dealing with are defined implicitly and do not cover the entirety of
> the cube's facets. Is there something in CGAL that would help do this?
> 
> However, I suppose my actual issue is being able to accurately specify
> boundary conditions. I was trying to make this easy by forcing the
> boundaries of the mesh to align with bounding cube.
> 
> With a triangulation generated by the periodic mesh package, is there
> a way to colour or otherwise somehow mark the cell faces on each
> boundary? I'm not sure this is a meaningful question given the
> irregular nature of the boundaries!
> 
> Sorry for the basic questions - I'm new to CGAL and still finding my way 
> around!
> 
> Many thanks,
> Matt
> 
> 
> On Tue, 16 Mar 2021 at 10:54, Monique Teillaud
> <> wrote:
>>
>> Dear Matthew,
>>
>> In fact, if you add points on the facets of the cube and you ensure that 
>> the
>> facets are triangulated as mael suggests, then you are enforcing the
>> periodicity through these points. You are not using the functionality that 
>> is
>> offered by the periodic mesh package.
>> In other words, this should rather be done with the non-periodic meshing
>> package.
>>
>> (In fact I would be curious why you need the facets to be triangulated... 
>> Our
>> algorithm is precisely designed to avoid adding such artificial points...)
>>
>> Best regards,
>> --
>> Monique Teillaud
>> https://members.loria.fr/Monique.Teillaud/
>> INRIA Nancy - Grand Est, LORIA
>> Institut National de Recherche en Informatique et Automatique
>>
>> ----- Le 15 Mar 21, à 17:21, cgal-discuss <> a écrit :
>>
>> Hi Mael,
>>
>> Thanks for your reply.
>>
>> It's a shame the periodic mesher can't do this currently. Would you be 
>> able to
>> give some hints on how to implement your idea of using the standard 3D mesh
>> package? I'm slightly wary about manually moving vertices around - won't 
>> this
>> reduce the quality of the resulting mesh?
>>
>> Thanks,
>> Matt
>>
>> On Mon, 15 Mar 2021, 08:04 Mael Rouxel-Labbé,
>> <> wrote:
>>>
>>> Hello,
>>>
>>> This is not currently possible in a straightforward manner in the
>>> periodic mesh generator, as there is no 3D constrained Delaunay
>>> triangulations in CGAL yet.
>>>
>>> In a less straight forward manner, if you wish your elements to lie
>>> exactly on the boundary of the periodic domain, you might be able to do
>>> away with the periodic mesh generation algorithm: generate a 3D mesh of
>>> the implicit function clipped by the periodic domain, and then ensure
>>> that the vertices are identical on both sides.
>>>
>>> Best,
>>> Mael
>>>
>>> On 15/03/2021 02:05, Matthew Russell ( via
>>> cgal-discuss Mailing List) wrote:
>>> > Dear all,
>>> >
>>> > I would like to generate periodic 3D meshes of regions bounded by
>>> > implicit functions and so I was pleased to find examples such as [1]
>>> > that do almost exactly what I want. The problem that I'm having is
>>> > that cells in the meshes generated from this example are able to lie
>>> > across the bounding unit cube, but to use the meshes in finite element
>>> > simulations I need the faces of the cells to align with the boundaries
>>> > of the cube.
>>> >
>>> > For example, the CGAL example [1] (with a different implciit function)
>>> > generates meshes like [cgal.jpg], but I would like one like
>>> > [gmsh.jpg].
>>> >
>>> > I haven't been able to find a way to do this in CGAL. Is it possible?
>>> >
>>> > Many thanks,
>>> > Matt
>>> >
>>> > [1]
>>> > https://doc.cgal.org/latest/Periodic_3_mesh_3/Periodic_3_mesh_3_2mesh_implicit_shape_8cpp-example.html
>>> >
>>>
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>>>
>>>
>>
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