[Gmsh] dilate to flatten a mesh

[Nathan J. Neeteson]

Hi Ricardo,

If the issue is simply that you have some vertices with non-zero z-components, and you want them to all be zero, and if the mesh file is ASCII format, could you just write a script (say, in python) to automatically loop through the $Nodes section of the file and replace the z component of every vertex position with "0.0" in a new file? I don't think any derived geometric data (such as cell areas or volumes) is in a *.mesh file, so naively I would think this should work, and the script in question would probably be no more than a few dozen lines.

Thanks,

Nathan Neeteson, M.Sc., E.I.T.
Flow Control Research Engineer
RGL Reservoir Management Inc.
Corporate Head Office
P 780.851.8243 | C 613.929.6283
nneeteson at rglinc.com | rglinc.com
API Q1™ and ISO 9001:2015 certified facilities.

-----Original Message-----
From: Ricardo Ruiz Baier [mailto:ricardo.ruiz.baier at gmail.com]
Sent: June 3, 2019 11:32 AM
To: Nathan J. Neeteson <nneeteson at rglinc.com>; Ricardo Ruiz Baier <ruizbaier at maths.ox.ac.uk>
Cc: gmsh at onelab.info
Subject: Re: [Gmsh] dilate to flatten a mesh

Dear Nathan,

thank you very much. This indeed resolves the syntax problem. However in my case it does not do anything since transformations can only be applied to the geometry, and in this case I want to apply the dilation to the mesh. I'll keep looking for other solutions.

All the best,

Ricardo

> Hi Ricardo,
>
> The syntax for anisotropic dilation is as follows:
>
> Dilate { { expression-list }, { expression, expression, expression } }
> { transform-list }
>
> The first expression-list is the homethetic center of the dilation.
>
> The set of three expressions are the X,Y,Z scaling factors of the dilation.
>
> The transform-list is the entities to be acted on.
>
> I think your syntax should be:
>
> Dilate{ {0,0,0}, {1,1,0} }{ Point{all_points[]}; }
>
> Assuming you want all points on the x-y plane at z=0.
>
> Nathan Neeteson, M.Sc., E.I.T.
> Flow Control Research Engineer
> RGL Reservoir Management Inc.
> Corporate Head Office
> P 780.851.8243 | C 613.929.6283
> nneeteson at rglinc.com | rglinc.com
> API Q1(tm) and ISO 9001:2015 certified facilities.
>
> -----Original Message-----
> From: gmsh [mailto:gmsh-bounces at ace20.montefiore.ulg.ac.be] On Behalf
> Of Ricardo Ruiz Baier
> Sent: June 3, 2019 5:51 AM
> To: gmsh at onelab.info
> Subject: [Gmsh] dilate to flatten a mesh
>
> Dear all,
>
> I have a .mesh triangulation which is supposed to be 2D. However it has some vertices with (spurious) crazy large z-components. How can I flatten these from e.g. a geo file?
>
> I've tried with "Dilate" in the manner mentioned below, but it does not work (the compilation complains about the syntax and I have not found any examples).
>
> Merge "testMesh.mesh";
>
> all_points[] = Point '*';
>
> Dilate { { all_points[] }, { 1, 1, 0} } {Surface(1) };
>
> Thank you so much!
>
> Kind regards,
>
>
>
> --
> Ricardo Ruiz Baier
> Mathematical Institute
> University of Oxford
> people.maths.ox.ac.uk/ruizbaier
>
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--
Ricardo Ruiz Baier
Mathematical Institute
University of Oxford
people.maths.ox.ac.uk/ruizbaier
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