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

[Nico Schlömer]

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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>>
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