Problem with element size.

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Problem with element size.

imperin
Hello everybody,
Can anyone explain me, why I have bad elements near the edges(
edge_size=facet_size=cell_size). As you can see on pic.1. elements in yellow
circle and in black circle are not the same. Can I fix it somehow? Why
elements near the edge are always taller than others?  
Thanks a lot
<http://cgal-discuss.949826.n4.nabble.com/file/t376139/element_size.jpg>



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Re: Problem with element size.

Sebastien Loriot (GeometryFactory)
Without much details, I can only guess that you have an issue with sharp
features as in this figure:

https://doc.cgal.org/latest/Mesh_3/index.html#fig__figuretwo_spheres_mesh


You should read this section:
https://doc.cgal.org/latest/Mesh_3/index.html#title31

to see how you can protect features.

Sebastien.

On 9/6/19 9:16 AM, imperin wrote:

> Hello everybody,
> Can anyone explain me, why I have bad elements near the edges(
> edge_size=facet_size=cell_size). As you can see on pic.1. elements in yellow
> circle and in black circle are not the same. Can I fix it somehow? Why
> elements near the edge are always taller than others?
> Thanks a lot
> <http://cgal-discuss.949826.n4.nabble.com/file/t376139/element_size.jpg>
>
>
>
> --
> Sent from: http://cgal-discuss.949826.n4.nabble.com/
>

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Re: Problem with element size.

imperin
I use detect_features() for the domain, but the output result is not so
good(See pic.1).

Mesh_domain domain(block1);
domain.detect_features();
Mesh_criteria criteria(edge_size = 0.005,                                                                                                                                                                                                                
   facet_angle = 30, facet_size = 0.005, facet_distance = 0.00000005,                                                                                                                                                                    
   cell_radius_edge_ratio = 2, cell_size = 0.005);                                                                                                                                                                                                                                                                                                                                                                                                  

// Mesh generation                                                                                                                                                                                                                
C3t3 c3t3 = CGAL::make_mesh_3<C3t3>(domain, criteria, lloyd(time_limit=3),
odt(time_limit=3),                                                                                                                                                                          
  perturb(time_limit=30, sliver_bound=30), exude(time_limit=30,
sliver_bound=30));



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Re: Problem with element size.

Sebastien Loriot (GeometryFactory)
The picture is small and I have no idea what is the input model.

Several possible cause for small elements:
- Feature not correctly detected
- the domain has a small local feature size:
   -- 2 sheets close together
   -- one feature close to a sheet
   -- ...

Sebastien.

On 9/6/19 9:43 AM, imperin wrote:

> I use detect_features() for the domain, but the output result is not so
> good(See pic.1).
>
> Mesh_domain domain(block1);
> domain.detect_features();
> Mesh_criteria criteria(edge_size = 0.005,
>     facet_angle = 30, facet_size = 0.005, facet_distance = 0.00000005,
>     cell_radius_edge_ratio = 2, cell_size = 0.005);
>
> // Mesh generation
> C3t3 c3t3 = CGAL::make_mesh_3<C3t3>(domain, criteria, lloyd(time_limit=3),
> odt(time_limit=3),
>    perturb(time_limit=30, sliver_bound=30), exude(time_limit=30,
> sliver_bound=30));
>
>
>
> --
> Sent from: http://cgal-discuss.949826.n4.nabble.com/
>

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