CGAL users discussion list

[Benjamin Kehlet <>]

Hi Jane

2014-10-13 17:25 GMT+02:00 Jane Tournois 
<>:
> Hi Benjamin,
>
> you are not doing anything wrong.
>
> As you have noticed, the mesh itself is the C3T3
> (Complex_3_in_triangulation_3).
> The C3T3 is a subset of the triangulation.
> So, there can be cells, and vertices, that belong to the triangulation, but
> not to the C3T3.
>
> In your particular example, the criteria that you are using to generate the
> mesh are a bit too weak. One symptom of that is that the surface is not very
> well fitted by the mesh. You can see it if you output the mesh to Medit for
> example.
>
> About isolated vertices, it's the same as for cells. It is not forbidden to
> have one or several vertices that belong to the triangulation but not to the
> triangulation.
> It can be the case for example when a vertex is first inserted on the
> boundary (let's say during the initialization step), but then the refinement
> process changes the connectivity around it, and the vertex can start not to
> belong to the boundary anymore.

Ah! I didn't know that could happen.

>
> To make it short :
> - it is not a bug
> - the object that are interested in at the end/during the mesh generation
> process is the C3T3

Thanks a lot for the explanation, Jane! That was very enlightening.

So just to be sure: It is then my responsibility to grab only the
relevant vertices from the triangulation, right? (Since the C3T3 does
not provide an iterator over the vertices that belong to the complex.)

Regards

Benjamin

>
> Best regards,
>
> Jane.
>
>
> --
> Jane Tournois, PhD
> R&D Engineer at GeometryFactory
> http://www.geometryfactory.com/
>
>
>
> Le 13/10/2014 10:41, Benjamin Kehlet a écrit :
>
>> 2014-10-13 9:55 GMT+02:00 Clément Jamin 
>> <>:
>>>
>>> Hi Benjamin,
>>>
>>> Do you use the *parallel* mesh algorithm that is available in CGAL 4.5
>>> (with CGAL::Parallel_tag)?
>>
>> Hello Clément!
>>
>> No, this is in serial.
>>
>> Regards
>>
>> Benjamin
>>
>>> Best,
>>> Clément.
>>>
>>>
>>> On Mon, Oct 13, 2014 at 12:44 AM, Benjamin Kehlet 
>>> <>
>>> wrote:
>>>>
>>>> Hello CGAL community!
>>>>
>>>> When meshing polyhedral domains, I sometimes experience isolated
>>>> vertices, ie. vertices which does not belong to any cell. The attached
>>>> file demonstrates the problem. Could someone take a look, and check if
>>>> I'm doing anything wrong? The code for reading out the mesh is based
>>>> on the code in CGAL for exporting to medit's file format.
>>>>
>>>> I get this result when attempting to mesh the file
>>>> demo/Polyhedron/data/rotor.off from CGAL's source tree:
>>>>
>>>> benjamik@benjamik-ThinkPad:~/tmp/cgal-meshing/build$ ./main
>>>> ~/software/CGAL-4.5/demo/Polyhedron/data/rotor.off
>>>>
>>>> [...]
>>>>
>>>> Number of unconnected vertices:14
>>>> 0.0693619 0.340288 -0.260398 0
>>>> 0.148692 0.344385 -0.252795 0
>>>> 0.11059 0.332426 -0.267569 0
>>>> 0.0800736 0.308173 -0.290017 0
>>>> 0.0358875 0.312982 -0.283919 0
>>>> 0.0739249 0.2902 -0.306196 0
>>>> 0.100469 0.304801 -0.293518 0
>>>> 0.0949104 0.318775 -0.276573 0
>>>> 0.0777684 0.350724 -0.248457 0
>>>> 0.0909964 0.338994 -0.261008 0
>>>> 0.0263695 0.298269 -0.299189 0
>>>> 0.00269295 0.307881 -0.290388 0
>>>> 0.0496229 0.300013 -0.297675 0
>>>> -0.0248875 0.311644 -0.285615 0
>>>>
>>>> Also a few other files (at least cow.off and bones.off and maybe
>>>> others) in the same directory reproduces the problem.
>>>>
>>>> Best regards
>>>>
>>>> Benjamin Kehlet
>>>>
>>>> --
>>>> You are currently subscribed to cgal-discuss.
>>>> To unsubscribe or access the archives, go to
>>>> https://sympa.inria.fr/sympa/info/cgal-discuss
>>>>
>>>>
>>> --
>>> You are currently subscribed to cgal-discuss.
>>> To unsubscribe or access the archives, go to
>>> https://sympa.inria.fr/sympa/info/cgal-discuss
>>>
>>>
>
>
>
> --
> You are currently subscribed to cgal-discuss.
> To unsubscribe or access the archives, go to
> https://sympa.inria.fr/sympa/info/cgal-discuss
>
>