Re: [Gmsh] [gmsh] "silly" question

[Max Orok]

Hi Alessandro,

The most straightforward way I can think of would be to use a CAD program
to make the 3D letters, export the model as STEP and then mesh that.
Tinkercad is one free option (I think you need to make an account).

There is an interesting script on Prof. Geuzaine's site (upper left corner)
for meshing a picture:
http://www.montefiore.ulg.ac.be/~geuzaine/

When I tried to use this script with a picture of text:
[image: image.png]

the result was extremely dense (the mesh lines are so dense they look solid
yellow), so it's not as easy as swapping out the picture, some further
tweaks are required to the background mesh scaling values probably.

[image: image.png]


Sincerely,
Max



On Wed, May 29, 2019 at 4:17 AM Alessandro Vicini <
alessandro.vic...@sitael.com> wrote:

>
>
> I would like to generate a 3d mesh for the volume obtained by extrusion of
> a text. So what I need to do is to import the text (as an image?) in gmsh,
> convert it somehow in a 2d geometry and then extrude it…
>
> Is this possible? Thank you.
>
>
>
> Alessandro
>
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-- 
Max Orok
Contractor
www.mevex.com
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Re: [Gmsh] nonmonotonic tags for nodes

[Christophe Geuzaine]

> On 22 May 2019, at 08:33, Christophe Geuzaine  wrote:
> 
> 
> Hi guys,
> 
> Indeed, currently we only renumber nodes and elements (if Mesh.Renumber is 
> set) at the end of the main mesh generation pipeline (Mesh 1, 2, 3). The 
> renumbering is not done when the order of the mesh is changed interactively 
> in the GUI, or when other mesh modifications are performed interactively 
> (refinement, adaptation, ...): the renumbering has to be performed explicitly 
> in those cases.
> 
> We could add the renumbering step for all these operations as well.

PS : this has been merged in master.


> What do you think?
> 
> Christophe
> 
> 
>> On 22 May 2019, at 04:43, G. D. McBain  wrote:
>> 
>> In https://github.com/nschloe/meshio/issues/388 ‘MSH 4.1: nodes have wrong 
>> tags in some cases’, it was reported that sometimes the nodes weren't tagged 
>> monotonically.
>> My reading of the specification was that this shouldn't happen:
>> 
>>By default, for non-partitioned, single file meshes, Gmsh will create 
>> files with a 
>>continuous ordering of node and element tags, starting at 1.
>> 
>> Is that right?
>> 
>> A simple two-dimensional GEO file, ordering.geo, attached and listed
>> 
>>SetFactory("OpenCASCADE");
>>Rectangle(1) = {0, 0, 0, 1, 0.5, 0};
>>Transfinite Curve {1, 2, 3, 4} = 3 Using Progression 1;
>> 
>> was provided that when run to produce 6-node triangles in the GUI didn't tag 
>> the nodes sequentially in the output MSH 4.1 file whereas it does when run 
>> from the command line with
>> 
>>   gmsh -2 -order 2 ordering.geo
>> 
>> The 'Transfinite Curve' doesn't affect the phenomenon, but omitting it here 
>> does increase the number of nodes and elements, so it's handy for keeping 
>> the output easier to inspect at a glance.
>> 
>> Specifically, in the $Nodes block, the one-dimensional entity blocks have 
>> deranged tags for the nodes; e.g., lines 30–33 of ordering-gui.msh, 
>> generated in the GUI, are
>> 
>> 1 1 0 3
>> 5
>> 11
>> 12
>> 
>> whereas in ordering-cl.msh, generated from the command line, they are
>> 
>> 1 1 0 3
>> 5
>> 6
>> 7
>> 
>> I guess meshio should be rewritten to cope with this, but I thought I'd 
>> report it here in case it was anomalous and unexpected.  
>> 
>> It was originally reported for Gmsh 4.2 and I've reproduced it with the 
>> latest git master, 4.4.0-git-bea1e5dde.
>> 
>> 
>> Sent from ProtonMail, Swiss-based encrypted email.
>> 
>> 
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> 
> — 
> Prof. Christophe Geuzaine
> University of Liege, Electrical Engineering and Computer Science 
> http://www.montefiore.ulg.ac.be/~geuzaine
> 
> 
> 
> 
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— 
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science 
http://www.montefiore.ulg.ac.be/~geuzaine




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[Gmsh] Creation of simple surface mesh

[Florian Lindner]

Hello,

I have an existing surface geometry, which is the Stanford bunny [1] as PLY 
format.

My goal is too evaluate a mapping algorithm on a non-trivial geometry. The 
algorithm works only on point data, therefore I don't need an triangulation.

>From the existing surface data I want to generate sampled points of various 
>densities on the surface of the geometry and save these as a standard data 
>format (e.g. VTK).

As I want to generate different mesh sizes, I need something like a background 
mesh size or a characteristic length which controls the sampling frequency. The 
exact placement of the points is not important, it should "make sense", i.e. be 
roughly equidistant or maybe influenced by the curvature.

So far I have only Merge "bun_zipper.ply"; in my .geo file. 

I think you can feel, that I am very uncertain how to progress and I would be 
very happy for guidance!

Thanks!
Florian


[1] http://graphics.stanford.edu/pub/3Dscanrep/bunny.tar.gz

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[Gmsh] [gmsh] "silly" question

[Alessandro Vicini]

I would like to generate a 3d mesh for the volume obtained by extrusion of a 
text. So what I need to do is to import the text (as an image?) in gmsh, 
convert it somehow in a 2d geometry and then extrude it...
Is this possible? Thank you.

Alessandro
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