[Paraview] unstructured grid, programmable filters: extract, process array data

[Andy Bauer]

Hmm, I tried extracting out the components using the Calculator filter and
then using the PythonCalculator filter to do that math.atan2 function.
Underneath the covers I believe there is a conversion from a vtkDataArray to
a numpy array and then back again.  I don't think this is getting done for
the math.atan2 function (it's not listed in the web page of python
calculator functions) so you may be stuck here unless someone else has an
idea.

Andy

On Wed, Feb 16, 2011 at 10:25 AM, Nico Schlömer <nico.schloemer at gmail.com>wrote:

> That sounds *exactly* like what I need. Great!
> I'm having problems selecting the data sets though: Where
> "atan(psi__Y/psi__X)" works with the calculator filter, "math.atan2(
> psi__Y, psi__X)" fails in the PythonCalculator with
>
> ============== *snip* ==============
> Traceback (most recent call last):
>  File "<string>", line 19, in <module>
>  File "<string>", line 27, in RequestData
> NameError: name 'psi__Y' is not defined
> ============== *snap* ==============
>
> I looked at http://www.paraview.org/Wiki/Python_Calculator but
> couldn't figure out what's wrong.
>
> --Nico
>
>
>
> On Wed, Feb 16, 2011 at 2:43 PM, Tim Gallagher <tim.gallagher at gatech.edu>
> wrote:
> > You can use the Python Calculator, which will let you use any valid
> Python expression -- such as math.atan2().
> >
> > Tim
> >
> > ----- Original Message -----
> > From: "Nico Schlömer" <nico.schloemer at gmail.com>
> > To: "Andy Bauer" <andy.bauer at kitware.com>
> > Cc: paraview at paraview.org
> > Sent: Wednesday, February 16, 2011 8:29:02 AM
> > Subject: Re: [Paraview] unstructured grid, programmable filters: extract,
> process array data
> >
> > Almost there!
> >
> >> atan(coordsX/coordsY)
> >
> > If instead of coordsX I use psi__{X,Y}, things work. However, I need
> > something slightly different than atan: I'd like to get the complex
> > argument of a complex number X+iY (i.e., the angle with the positive
> > real axis). It's quite ~similar~ to what atan does, see for example
> > <http://gcc.gnu.org/onlinedocs/gcc-4.0.4/gfortran/ATAN2.html>. In
> > Python, the function is called math.atan2() as well.
> > ParaView's  calculator filter does however not support atan2(), and
> > that was my original motivation to look at programmable filters
> > actually. Well, it'd be much nicer if the same thing could be done
> > with the calculator of course!
> > Workarounds?
> >
> > --Nico
> >
> >
> >
> >
> >
> > On Tue, Feb 15, 2011 at 6:56 PM, Andy Bauer <andy.bauer at kitware.com>
> wrote:
> >> This sounds like a job for the calculator filter.  "coordsX^2+coordsY^2"
> for
> >> your first example (or "psi__X^2+psi__Y^2" for the psi variables) and
> >> "atan(coordsX/coordsY)" for the second example.
> >>
> >> It can operate on point or cell data (set in the Attribute Model
> drop-down
> >> menu), replace invalid numbers with a specified value, and you can name
> the
> >> resulting array as well.
> >>
> >> Andy
> >>
> >> 2011/2/15 Nico Schlömer <nico.schloemer at gmail.com>
> >>>
> >>> Hi all,
> >>>
> >>> I've been looking at
> >>> <http://www.paraview.org/Wiki/Python_Programmable_Filter> to create a
> >>> programmable filter, but I'm a bit lost as to whether or not I need
> >>> GetPolyData, CopyAttributes,...
> >>>
> >>> Essentially, I have an unstructured grid in an ExodusII file (like the
> >>> attached file actually) with point data "psi" in it that has two
> >>> components (X,Y). I can plot psi:X, psi:Y, and psi:magnitude alright
> >>> with the default GUI options, but what I would really like to have
> >>> plotted is X^2+Y^2 (no sqrt()) and something along the lines of
> >>> arctan(Y/X).
> >>>
> >>> Is there simple code somewhere some that takes array data off of an
> >>> unstructured grid, does something with it and returns the extra array
> >>> from the filter?
> >>>
> >>> Cheers,
> >>> Nico
> >>>
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