[Gmsh] Gmsh-4.0.4 Volume mesh issue

[Simone GREMMO]

Dear Christophe,

as you asked in your previous email, I have been testing the newly implemented quad-boundary recovery in Gmsh (at that time it was the development version, future 4.0.5 or 4.1).


I found that Gmsh works fairly well, succeeding to generate a valid mesh with sufficient overall quality (a few ill-shaped elements may be present depending on the geometry configuration).

However, in some cases, the resulting mesh has a negative cell. All the failing cases have one negative cell only, this cell always being a flat pyramid (see attached picture). It looks like the vertex relocation cannot move the top of the pyramid inside the volume.


Does anyone have reported a similar behaviour?

If necessary, I can provide you with a failing test case.


Regards,

Simone G.

________________________________
From: Christophe Geuzaine <cgeuzaine at uliege.be>
Sent: Monday, November 12, 2018 3:33:25 PM
To: Simone GREMMO
Cc: gmsh at onelab.info
Subject: Re: [Gmsh] Gmsh-4.0.4 Volume mesh issue


Dear Simone,

Indeed, Gmsh 4.0.0 -> 4.0.4 do not have the ability to automatically create hybrid tetrahedral+pyramidal meshes (your surface contains quadrangles).

The latest snapshot (future Gmsh 4.0.5 or Gmsh 4.1) has a new algorithm to generate such meshes, similar but more general to what we did in Gmsh 3. Give it a try and let us know how it works out for you?

Christophe


> On 12 Nov 2018, at 14:38, Simone GREMMO <Simone.GREMMO at umons.ac.be> wrote:
>
> Dear all,
> I have just downloaded the last version of Gmsh (4.0.4), but I am facing a problem with the generation of a "simple" volume mesh.
>
> I would like to mesh a volume delimited by a surface mesh in .msh format, but it looks like Gmsh cannot create the volume mesh.
> Error Message is :
> .....
> Info    : Boundary Recovery...
> Info    : Writing to GRegion...
> Info    : Reconstruct time : 0.116395 sec
> Error   : No tetrahedra in region 5
> Info    : 3D point insertion terminated (3195 points created):
> Info    :  - 0 Delaunay cavities modified for star shapeness
> Info    :  - 0 points could not be inserted
> Info    :  - 0 tetrahedra created in 1.6e-05 sec. (0 tets/sec.)
> Error   : No tetrahedra in region 5
> Info    : Done meshing 3D (0.133228 s)
> Info    : 4857 vertices 6617 elements
> Error   : ------------------------------
> Error   : Mesh generation error summary
> Error   :     0 warnings
> Error   :     2 errors
> Error   : Check the full log for details
> Error   : ------------------------------
>
> I am attaching the .geo file I have created as well as the surface mesh I used. To launch the mesh generation I run the command:
> gmsh-4.0.4 createGeom.geo -3 -o volumeMesh.msh
>
> Note that the same test case is successfully meshed using Gmsh version 3.0.6.
>
> Do you have any suggestion on how to solve the problem?
> Is it possible that the surface mesh, containing both triangles and quadrangles is at the origin of the problem?
>
> Thanks in advance for your suggestions.
> Regards,
> Simone G.
>
> <createGeom.geo><surfaceMesh.msh>_______________________________________________
> gmsh mailing list
> gmsh at onelab.info
> http://onelab.info/mailman/listinfo/gmsh
gmsh Info Page<http://onelab.info/mailman/listinfo/gmsh>
onelab.info
Gmsh is a free 3D finite element mesh generator with built-in pre- and post-processing facilities. This list is for questions and discussions about Gmsh features, resources, bugs, and so forth. Useful links: Gmsh homepage (for documentation, downloads, etc.); gmsh-announce mailing list (for announcements about new Gmsh releases and major bug fixes - you probably want to subscribe to that, as well)



—
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science
http://www.montefiore.ulg.ac.be/~geuzaine

Free software: http://gmsh.info | http://getdp.info | http://onelab.info

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://onelab.info/pipermail/gmsh/attachments/20181217/74fb1228/attachment-0001.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: negCell_.jpg
Type: image/jpeg
Size: 726202 bytes
Desc: negCell_.jpg
URL: <http://onelab.info/pipermail/gmsh/attachments/20181217/74fb1228/attachment-0001.jpg>