[Paraview] Gradient of 2D velocity field with paraview

[Andy Bauer]

Hi,

The Extract Surface filter will subdivide the quadratic triangles into 4
linear triangles so the resulting field will likely lose some accuracy but
not as bad as just going from a quadratic triangle to a linear triangle. I
added in a bug for our bug tracker at
http://www.paraview.org/Bug/view.php?id=15299 so that gradients can be
computed properly for quadratic triangles. I don't have an estimate of when
this may get fixed though. If this is urgent enough, this is open-source
software so you can try fixing it yourself and sending in a patch.
Otherwise, Kitware does provide support contracts for fixing such bugs (see
http://www.kitware.eu/products/support.html for more info).

Regards,
Andy

On Sun, Feb 1, 2015 at 5:30 AM, Eleonora Piersanti <
eleonorapiersanti at yahoo.it> wrote:

> Sorry to bother you again. But I need the gradient to make some
> verifications in my code. Then, the problem of accuracy is quite important.
> Is there any way to compute the gradient without using the Extract surface
> filter?
>
> Kind regards,
> Eleonora
>
>
>   Il Venerdì 30 Gennaio 2015 11:48, Andy Bauer <andy.bauer at kitware.com>
> ha scritto:
>
>
> It looks like the Gradient of Unstructured Data Set filter isn't working
> properly with quadratic triangles. Try using the Extract Surface filter
> before computing gradients to convert them into linear triangles.
>
> If you want to get more familiar with using ParaView, the ParaView
> tutorial at http://www.paraview.org/Wiki/The_ParaView_Tutorial is a good
> place to start.
>
> Regards,
> Andy
>
> On Fri, Jan 30, 2015 at 6:25 AM, Eleonora Piersanti <
> eleonorapiersanti at yahoo.it> wrote:
>
> Thank you for the answer.
> I think that the dimension of the .vtk file was too big. You can download
> the .vtk file from:
>
>
> https://www.dropbox.com/s/o1wjo2brsaeu5ag/stability_realEigU_up0.vtk.tar.gz?dl=0
>
> In which sense should I use the Slice filter? Sorry but I am quite new
> with paraview.
> Kind regards,
> Eleonora
>
>    Il Venerdì 30 Gennaio 2015 11:16, Eleonora Piersanti <
> eleonorapiersanti at yahoo.it> ha scritto:
>
>
> Thank you, for the answer.
> I attach the .vtk file. In which sense should I use the Slice filter?
> Sorry but I am quite new with paraview.
> Kind regards,
> Eleonora
>
>
>   Il Venerdì 30 Gennaio 2015 10:59, Andy Bauer <andy.bauer at kitware.com>
> ha scritto:
>
>
> Your description is a bit vague to diagnose the issue. Can you share your
> data set? I was able to use the Wavelet source, use the Slice filter and
> then use the Gradient of Unstructured Data Set without any issues. Can you
> see if that works for you?
>
> Regards,
> Andy
>
> On Fri, Jan 30, 2015 at 5:26 AM, Eleonora Piersanti <
> eleonorapiersanti at yahoo.it> wrote:
>
> Hi to everyone!
> I computed with finite elements a 2D velocity field. I plotted without any
> problem the velocity field with paraview. I would like to compute the
> gradient.
> I tried Filters->Gradient of Unstructured Data Set but without succes.
> Can you help me?
> Thanks,
> Nora
>
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