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

[Tim Gallagher]

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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