CGAL Is there a way to slice the mesh and check the connectivity?

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CGAL Is there a way to slice the mesh and check the connectivity?

Frank Dz
This post was updated on .
Hi, I want to ask is there a method for us to slice a mesh by setting a set
of points (or: a loop/ a set of edges) and have a connectivity check on the
mesh.

For example, the following loop cut the mesh, yet the connectivity is still
1.


Another example is the following that two loops cut the mesh and the
connectivity is 2.
<http://cgal-discuss.949826.n4.nabble.com/file/t376165/snapshot00.png

Best,
Frank



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Re: CGAL Is there a way to slice the mesh and check the connectivity?

Sebastien Loriot (GeometryFactory)
The two pictures are the same.

Sebastien.

On 2/12/20 10:49 AM, Frank Dz wrote:

>
> Hi, I want to ask is there a method for us to slice a mesh by setting a set
> of points (or: a loop/ a set of edges) and have a connectivity check on the
> mesh.
>
> For example, the following loop cut the mesh, yet the connectivity is still
> 1.
> <http://cgal-discuss.949826.n4.nabble.com/file/t376165/snapshot00.png>
>
> Another example is the following that two loops cut the mesh and the
> connectivity is 2.
> <http://cgal-discuss.949826.n4.nabble.com/file/t376165/snapshot00.png>
>
> Best,
> Frank
>
>
>
> -----
> be open, be creative, be critical
> --
> Sent from: http://cgal-discuss.949826.n4.nabble.com/
>

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Re: CGAL Is there a way to slice the mesh and check the connectivity?

Frank Dz
Sorry for the confusion. Updated.

Thanks!





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Re: CGAL Is there a way to slice the mesh and check the connectivity?

Frank Dz
I'd better resend it :


figure 1 (connectivity:1)
<http://cgal-discuss.949826.n4.nabble.com/file/t376165/snapshot000.png>

figure 2 (connectivity:2)
<http://cgal-discuss.949826.n4.nabble.com/file/t376165/snapshot00.png>



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Re: CGAL Is there a way to slice the mesh and check the connectivity?

Frank Dz
In reply to this post by Sebastien Loriot (GeometryFactory)
I also noted that in https://doc.cgal.org/latest/Surface_mesh/index.html
there is a description of the half-mesh connectivity:

>The connectivity is also stored in properties, namely the properties named
"v:connectivity", >"h:connectivity", and "f:connectivity". It is quite
similar for the marker of deleted element, where we have >"v:removed",
"e:removed", and "f:removed".


 but it is about the connection among the data structure not the
connectivity of the graph.





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Re: CGAL Is there a way to slice the mesh and check the connectivity?

Sebastien Loriot (GeometryFactory)
You can have a look at the function connected_components():
https://doc.cgal.org/latest/Polygon_mesh_processing/group__keep__connected__components__grp.html#gabe2052b2281e1e628e68d8fea94be2d9

Adding your yellow edges as constrained in the edge_is_constrained_map
named parameter will give you the number of components.

Best regards,

Sebastien.

On 2/12/20 1:04 PM, Frank Dz wrote:

> I also noted that in https://doc.cgal.org/latest/Surface_mesh/index.html
> there is a description of the half-mesh connectivity:
>
>> The connectivity is also stored in properties, namely the properties named
> "v:connectivity", >"h:connectivity", and "f:connectivity". It is quite
> similar for the marker of deleted element, where we have >"v:removed",
> "e:removed", and "f:removed".
>
>
>   but it is about the connection among the data structure not the
> connectivity of the graph.
>
>
>
>
>
> -----
> be open, be creative, be critical
> --
> Sent from: http://cgal-discuss.949826.n4.nabble.com/
>

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Re: CGAL Is there a way to slice the mesh and check the connectivity?

Frank Dz
Great! Thanks! I will have a try.

Actually I am currently using the dual relationship to check the
connectivity. I also add an answer in:
https://stackoverflow.com/questions/21502416/splitting-mesh-into-connected-components-in-openmesh/60219533#60219533
<https://stackoverflow.com/questions/21502416/splitting-mesh-into-connected-components-in-openmesh/60219533#60219533>  

It also works well for me.

Best,
Frank



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