Re: Calculations on data on triangular mesh.

[Juan Pablo Carbajal]

On Thu, Oct 25, 2012 at 9:03 PM, Richard <address@hidden> wrote:
> On 25/10/2012 18:57, Juan Pablo Carbajal wrote:
>>
>> On Thu, Oct 25, 2012 at 4:25 PM, Richard Crozier <address@hidden>
>> wrote:
>>>
>>> Hi,
>>>
>>> I want to do some post-processing of data generated using a 2D finite
>>> element code. The code produces the nodal quantities of the solution on a
>>> delauney triangulation. The data I have in the solution are the vertex
>>> locations, a map of these vertices for the triangles and values of the
>>> solution at the vertices.
>>>
>>> What I would like to know is, is there a library of functions for
>>> efficiently working with this kind of data? The kind of operations I am
>>> interested in are interpolation at arbitrary points, integration over
>>> regions of the triangulation, getting triangle areas, centroids etc etc.
>>> I
>>> would like to avoid writing all this code from scratch.
>>>
>>> I have looked around for this on Octave Forge and so on, but haven't come
>>> across anything appropriate yet.
>>>
>>> The code in question by the way is freely available and hosted here:
>>>
>>> https://sourced.ecdf.ed.ac.uk/projects/see/xfemm
>>>
>>> It is a mex interface I have created to the core C++ magnetics solver
>>> from
>>> this program:
>>>
>>> http://www.femm.info/wiki/HomePage
>>>
>>>
>>>
>>>
>>> --
>>> View this message in context:
>>> http://octave.1599824.n4.nabble.com/Calculations-on-data-on-triangular-mesh-tp4645732.html
>>> Sent from the Octave - General mailing list archive at Nabble.com.
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>>
>> Hi Richard,
>>
>> Thank you for your link. Are you in contact with the developer of
>> FEMM. I also use it but since it is not licensed under a
>> GPL-compatible license we cannot add an interface in Octave Forge.
>>
>> You may find the packages msh, fpl and geometry relatively useful.
>> There is many functionality missing and it would be great if you
>> develop anything missing that you share it we us.
>>
>> To interpolate in a triangular mesh you could build the trick with
>> griddata, but the best is to write your own bilinear interpolation (if
>> that is what you want) on the triangles. I have code but is not
>> documented. I can share if you want, but I do not promise good quality
>> :D. Indeed... I may wrote a function to interpolate on a triangular
>> mesh after the 29th...
>>
>> I am forwarding Carlo who is the one actively developing most of the FEM
>> tools.
>>
>
> Juan,
>
> I am in contact occasionally with the FEMM author, but he was not interested
> in my proposal which was to let me use my modified version of the magnetics
> solver code under an LGPL licence. I don't know if the FEMM author would be
> any more interested in the full GPL or another licence. In any case it uses
> Triangle (made by Jonathan Shrewchek) which is provided under similar terms
> to FEMM.
>
> If you use FEMM, you might find my code useful, I have made a function
> (writefemmfile.m) which can output a file in FEMM's input format given a
> problem definition stored as a normal Octave/Matlab structure. The FEMM
> solver C++ code can also be compiled as a standalone executable as well as a
> mexfunction. The mexfunction works with Octave, too. My 'interface'
> mexfunction though really just calls the FEMM code with a string containing
> the name of .fem file. I have replaced all the Windows-only MFC code with
> standard C++ so it can also be compiled on linux, and doesn't require Wine.
> I have also created a lot of helper functions in m-code for creating the
> problem structure (e.g. addnode_mfemm.m, addsegment_mfemm.m and similar).
> These are analagous to the existing OctaveFEMM interface code.
>
> Note this is only the magnetics solver though.
>
> I want to implement all the post-processing capabilities of FEMM, but in
> Matlab and Octave compatible code. All mcode I have written for
> pre-processing (problem definition) and post-processing is released under
> the Apache V2.0 licence. The modified FEMM sources are provided under an
> Aladdin Free Public Licence.
>
> At some point in the long term future I can consider replacing the actual
> solver code as well with something with a less restrictive licence. The
> alternative is to write a magnetics solver for FAESOR which is a 3D GPL
> finite element package for Matlab (haven't tested this extensively in
> Octave, but I'm pretty sure it works, apart from some visualisation code.).
> You can find FAESOR here:
>
> http://hogwarts.ucsd.edu/~pkrysl/faesor/faesor_publish.html
>
> In case you are interested. If you would like to help make the
> post-processing code for my FEMM interface, you, or anyone else are more
> than welcome!
>
> Richard
>
>
>
>
>
>
>
>
> --
> The University of Edinburgh is a charitable body, registered in
> Scotland, with registration number SC005336.
>

Hi Richard,

Yeah, I also contact Meeks once but couldn't get it under a free
compatible license. I think he is using some other code that he can't
release. Anyways...

I will definitely take a look at your code. Though post-processing is
not the exiting task for me (I mean there is so much already freed out
there, paraview for example, though I am not sure if the license is
truly free, but looks like BSD to me), please keep me updated. I am
already with too many projects, but who knows maybe I drop some of
them.

Thanks!