Add integrate_data filter

[MatthewFlamm]

Overview

Closes #2789 . Adds ability to integrate data in a dataset including area or volume.

Details

The vtk class vtkIntegrateAttributes includes a SetDivideAllCellDataByVolume() method, but I have deliberately chosen not to implement it and in fact have explicitly turned it off. When enabled, only the integrated cell data is divided by the area or volume. This could be confusing, and it is straightforward for the user to implement themselves.

The return from this filter is a bit weird at first, an UnstructuredGrid with 1 point and 1 cell. I considered returning a dict, e.g. {"data": 99.1, "Area": 2.45}. But given that we can have name clashes between point and cell data arrays, we'd have to return two dicts. So I have chosen to keep the default vtk behavior, and tried to explain this multiple times in the documentation and examples.

[codecov]

Codecov Report

Merging #2790 (3d06a2f) into main (b4abf24) will increase coverage by 0.00%.
The diff coverage is 100.00%.

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##             main    #2790   +/-   ##
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  Coverage   93.91%   93.91%           
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  Files          76       76           
  Lines       16298    16305    +7     
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+ Hits        15306    15313    +7     
  Misses        992      992           

[MatthewFlamm]

I intended to add to the gallery example one that uses a volume, but I ran out of implementation scheme steam. This might be a good 'first issue' that we can add.

[tkoyama010]

Thank you for adding this.

[akaszynski]

Thanks for adding this!

Extended this example with a simple volume example.

LGTM.

[tkoyama010]

LGTM