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[Zesen Qian <>]

OK so I just rewrote the program to use Mesh_3. One problem I
encountered is that I want to restrict the output mesh to be manifold,
but the named parameters doesn't seem to work.  It told me:

/home/riaqn/codes/cxx/offset.cxx:65:102: error: ‘manifold’ was not
declared in this scope
   base<T>::Meshing::C3t3 c3t3 = CGAL::make_mesh_3<typename
base<T>::Meshing::C3t3>(domain, criteria,
manifold=params::manifold());

it seems that there isn't such a named parameter in make_mesh_3's signature?

Best,
Zesen


On Wed, May 23, 2018 at 2:57 AM, Sebastien Loriot (GeometryFactory)
<>
 wrote:
>
>
> On 05/22/2018 08:33 PM, Zesen Qian wrote:
>>
>> Hi Sebastien,
>>
>> Thanks for this. I wrote the program myself and I'm using surface_mesh
>> instead of mesh_3. Question: Why will Mesh_3 be faster? From what I
>> understand this will not only generate facets but also cells inside
>> the shape? How will that accelerate the process?
>
> Mesh_3 code has been updated to take advantage of threads so it will be
> faster. Moreover, the code of Surface_mesh has not been updated for some
> time now because we are planning to replace it with the implementation of
> Mesh_3. If you put no constraints on the tetrahedra, only the constraints on
> surface facets will make the mesh work more.
>
> Sebastien.
>
>
>>
>> And in particular, if I'm not interested in the cells, how should I
>> set the parameters concerning it? i.e., cell_radius_edge_ratio and
>> cell_size.
>>
>> Best,
>> Zesen
>>
>> On Tue, May 22, 2018 at 2:25 PM, Sebastien Loriot (GeometryFactory)
>> <>
>>  wrote:
>>>
>>> Note that this PR : https://github.com/CGAL/cgal/pull/3043
>>> will bring some noticeable speed up as well as parallel mesh algorithm.
>>>
>>> Best,
>>>
>>> Sebastien.
>>>
>>>
>>> On 05/22/2018 07:18 PM, Zesen Qian wrote:
>>>>
>>>>
>>>> Hi Sebastien,
>>>>
>>>> Sorry for keep spamming your inbox - but I found how to sample areas
>>>> differently based on variety. For future reference, the parameter
>>>> distance_bound constrols the max distance from every generated facet
>>>> to the surface. So when the same value applies to different areas, the
>>>> areas with more details will get sampled more.
>>>>
>>>> Thank you so much for the help!
>>>>
>>>> Best,
>>>> Zesen
>>>>
>>>> On Tue, May 22, 2018 at 11:11 AM, Zesen Qian 
>>>> <>
>>>> wrote:
>>>>>
>>>>>
>>>>> Hi Sebastien,
>>>>>
>>>>> I think I was mistaken - I tried it again and it seems that I don't
>>>>> have to do too much about the angle_bound - adjusting other parameters
>>>>> would suffice to give a decent result.
>>>>>
>>>>> However, it is indeed slow. One feature of my mesh is that it donsn't
>>>>> have to be evenly sampled - some areas require more details than
>>>>> others.  Can I do some trick so that those area receive extra
>>>>> sampling, while other more monotone area get less, so I can save some
>>>>> processing time?
>>>>>
>>>>> Best,
>>>>> Zesen
>>>>>
>>>>> On Tue, May 22, 2018 at 10:26 AM, Zesen Qian 
>>>>> <>
>>>>> wrote:
>>>>>>
>>>>>>
>>>>>> Hi Sebastien,
>>>>>>
>>>>>> Thanks for this. I don't know if that's a similiar thing, but I tried
>>>>>> https://doc.cgal.org/latest/Surface_mesher/
>>>>>> by a distance function(with AABB_tree and side_of_triangle). Seen from
>>>>>> the source code of the plugin, it's very similar.
>>>>>>
>>>>>> To get a decent result it's quite slow. If I set the angular bound to
>>>>>> 90 degree(more than 30),  the algorithm is not garanteed to
>>>>>> terminate(and indeed in my case). My mesh has some very thin layers
>>>>>> that's easy  to be ignored by meshing, so I don't expect this method
>>>>>> to work.
>>>>>>
>>>>>> What I'm now trying is simply using the "solidify" modifier in
>>>>>> Blender, and fix the potential self-intersections using refining and
>>>>>> outer-hull operation, and then use boolean operation with the original
>>>>>> mesh to get a offseted mesh. I'm using libigl to do these tasks.
>>>>>>
>>>>>> Best,
>>>>>> Zesen
>>>>>>
>>>>>> On Tue, May 22, 2018 at 9:59 AM, Sebastien Loriot (GeometryFactory)
>>>>>> <>
>>>>>>  wrote:
>>>>>>>
>>>>>>>
>>>>>>> There is indeed nothing official in CGAL. However, in the Polyhedron
>>>>>>> demo we wrote a small plugin that is meshing the distance function to
>>>>>>> a
>>>>>>> mesh
>>>>>>> and the output is by construction guaranteed to be free from
>>>>>>> self-intersections. However sharp features are not correctly meshed
>>>>>>> if
>>>>>>> not protected.
>>>>>>>
>>>>>>> Go into 3D Surface Mesh Generation -> Offset meshing once having
>>>>>>> loaded
>>>>>>> a polyhedron.
>>>>>>>
>>>>>>> Source code is here:
>>>>>>>
>>>>>>>
>>>>>>> https://github.com/CGAL/cgal/blob/releases/CGAL-4.12-branch/Polyhedron/demo/Polyhedron/Plugins/Surface_mesh/Offset_meshing_plugin.cpp
>>>>>>>
>>>>>>> HTH,
>>>>>>>
>>>>>>> Sebastien.
>>>>>>>
>>>>>>>
>>>>>>> On 05/17/2018 07:44 PM, Zesen Qian wrote:
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> Hi list,
>>>>>>>>
>>>>>>>> I have a triangulated, closed mesh which is free of any
>>>>>>>> degeneracies.
>>>>>>>> Is there any reliable way to offset this mesh? By reliable I mean
>>>>>>>> the
>>>>>>>> result mesh should be free of any degeneracies.
>>>>>>>>
>>>>>>>> I searched on Internet and there is simply not an library/program
>>>>>>>> available that can do this. I guess CGAL isn't capable of this
>>>>>>>> either,
>>>>>>>> but I believe people on this list should be familiar with this topic
>>>>>>>> and maybe offer some comments.
>>>>>>>>
>>>>>>>> Thank you.
>>>>>>>>
>>>>>>>> Best,
>>>>>>>> Zesen
>>>>>>>>
>>>>>>>
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>>>>>>>
>>>>
>>>
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>>>
>>
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