[Paraview] programmable access to vector components (via Python)

[Fabian Wein]

@Utkarsh: I agree, it seems to be the same bug

@Berk: Thank you very much, that pushed me to solve the problem.

Currently it does not work work with our own filter (CellData is not 
known) but
when I export to vtk and read it works.

Currently I still work on the details of the python algorithm but in 
principal it works.

Anyway, any hint on what is missing for our own plugin reader?

Fabian

> I think this might be same as the bug: http://paraview.org/Bug/view.php?id=12951
>
> Utkarsh
>
> On Fri, May 25, 2012 at 4:13 PM, Berk Geveci<berk.geveci at kitware.com>  wrote:
>> Which version of ParaView is this? This bug sounds very familiar to me and I
>> vaguely remember sitting down with Utkarsh to fix it. If it is an older
>> version, can you try 3.14?
>>
>> As for the Python notation, take a look at:
>>
>> http://paraview.org/Wiki/ParaView/Users_Guide/Python_Programmable_Filter
>> http://paraview.org/Wiki/ParaView/Users_Guide/Python_Calculator
>>
>> You need to use something like: inputs[0].CellData['mechTensor'][:, n]
>> where n is whichever component that you are accessing. This notation is
>> based on Numpy. You can learn more about it here:
>>
>> Guide to NumPy - Trelgol
>>
>> Note that NumPy is much more powerful and efficient that the Array
>> Calculator so I'd recommend using the Python Calculator or the Python
>> Programmable Filter whenever possible.
>>
>>
>> -berk
>>
>>
>> On Fri, May 25, 2012 at 10:03 AM, Fabian Wein
>> <fabian.wein at am.uni-erlangen.de>  wrote:
>>>>
>>>> It appears to me you have found a limitation (or bug?) in the
>>>> Calculator filter. My comments are inserted below.
>>>
>>>
>>> I just submitted a bug report: http://paraview.org/Bug/view.php?id=13204
>>>
>>>
>>>> files, however, I have never used it. I graduated from VTK
>>>> XML-structured ASCII-text results files to the EnSight
>>>> binary-formatted specification in order to get compact, manageable
>>>> file-sets for my modestly large explicit transient dynamic simulations.
>>>
>>>
>>> We are happy with HDF5 but this requires a own reader plugin for
>>> our format which we wrote some years ago. With HDF5 we have also access
>>> via Matlab, with is a plus for us.
>>>
>>>
>>>> If the error message reflects a "limitation" in the Calculator, then
>>>> the Calculator only processes scalars and vectors (1st-order tensors),
>>>> and that in itself is no small accomplishment.
>>>
>>>
>>> My "mechTensor" is just a vector with 6 components, so the limitation is
>>> with the size of the vector.
>>>
>>> This answers two of my questions:
>>>
>>>
>>>> * am I right with the assumption, that the calculator does not like
>>>> double characters after the underline?
>>>> * Is this XX, YY, ... coming from Paraview?
>>>
>>>
>>> Anyone who can help me with the following two?
>>>
>>>
>>>> * How do I access the vector components via python?
>>>> * Where can I find more information about the python interface?
>>>
>>>
>>> Thanks a lot,
>>>
>>> Fabian
>>>
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