[Gmsh] Not getting a volume mesh

[Wayne Christopher]

Hi Ruth,

I'm able to get a volume mesh for some objects, but I'm finding that for 
others I'm getting:

Error   : Self intersecting surface mesh, computing intersections (this 
could take a while)
Error   : Surface mesh is wrong, cannot do the 3D mesh

and

Error:  Invalid PLC.
   Facet (41, 172, 188) (3749) is not a valid polygon.

An example is attached - command line is

gmsh try3.geo -3 -format msh -saveall -smooth 3 -o try3-out.gmsh

If I change the geometry somewhat it works fine, which makes me think 
there is some problem with the edges of the surfaces.  In general I 
can't force the triangulation on the geometry surfaces to match on 
curved edges where they meet, and I can see there are small gaps between 
the triangulations (small compared to the mesh I want).

Is this causing the problem?  Would it help if I specified what edges 
are adjacent to what surfaces, or provided some kind of tolerance?

Thanks,

     Wayne

On 3/25/12 12:05 AM, Ruth V. Sabariego wrote:
> Hi Wayne,
> For that you have to reclasify the elements of your geometry and 
> create the volume with the new surfaces.
>
> Try this:
> **********************
> Mesh.RemeshAlgorithm=1; //(0) nosplit (1) automatic (2) split only 
> with metis
>
> Merge "try1-geom.gmsh";
> RefineMesh;
> CreateTopology;
>
> ll[] = Line "*";
> For j In {0 : #ll[]-1}
>   Compound Line(newl) = ll[j];
> EndFor
>
> ss[] = Surface "*";
> For j In {0 : #ss[]-1}
>   ssn[] += news ;
>   Compound Surface(news) = ss[j];
> EndFor
>
>
> Surface Loop(10) = { ssn[] };
> Volume(11) = {10};
>
> Physical Volume("Cylinder.2") = {11};
> **********************
>
>
> Regards,
> Ruth
>
> --
> Dr. Ir. Ruth V. Sabariego
> University of Liege, Electrical Engineering & Computer Science,
> Applied & Computational Electromagnetics (ACE),
> phone: +32-4-3663737 - fax: +32-4-3662910 - 
> http://ace.montefiore.ulg.ac.be/
>
>
>
> On 24 Mar 2012, at 23:41, Wayne Christopher wrote:
>
>> Hi Ruth,
>>
>> Thanks - that fixes my volume problem.
>>
>> My other problem remains, though.  I want to define geometry using a 
>> msh file, and then create a mesh with new surface elements, not the 
>> ones I am using for geometry surfaces.    Is there a way to do this?
>>
>>     Wayne
>>
>> On 3/23/12 2:09 PM, Ruth V. Sabariego wrote:
>>> Hi Wayne,
>>>
>>> You need to define the geometrical Volume:
>>> Volume(11) = {10};
>>> the Physical Volume is used just for tagging the elements and their 
>>> further use in a e.g. FE solver.
>>>
>>> Regards,
>>> Ruth
>>>
>>> --
>>> Dr. Ir. Ruth V. Sabariego
>>> University of Liege, Electrical Engineering & Computer Science,
>>> Applied & Computational Electromagnetics (ACE),
>>> phone: +32-4-3663737 - fax: +32-4-3662910 - 
>>> http://ace.montefiore.ulg.ac.be/
>>>
>>>
>>>
>>> On 23 Mar 2012, at 18:41, Wayne Christopher wrote:
>>>
>>>> I'm trying to mesh a volume defined by surfaces that are defined by 
>>>> tessellations.  I don't want the mesh to be based on the surface 
>>>> triangles - those are purely geometry and in most cases finer than 
>>>> the volume mesh that I want.
>>>>
>>>> When I run gmsh like this:
>>>>
>>>> gmsh try1.geo -3 -format msh -saveall -smooth 3 -o try1-out.gmsh
>>>>
>>>> (files attached) I do not get any tetras in the output, and it 
>>>> appears that the output mesh is a refinement of the input mesh.
>>>>
>>>> What am I doing wrong?  Thanks,
>>>>
>>>>    Wayne
>>>>
>>>> <try1.geo><try1-geom.gmsh><try1-out.gmsh>_______________________________________________
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>>>> gmsh at geuz.org <mailto:gmsh at geuz.org>
>>>> http://www.geuz.org/mailman/listinfo/gmsh
>>>
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