[Paraview-developers] gradient filters

[Andy Bauer]

I'm looking at the 2 gradient filters available in the ParaView GUI and
trying to improve their functionality.  I see that the "Gradient of
Unstructured DataSet" filter only works with vtkPointSets in ParaView but in
general can handle vtkImages and vtkRectilinearGrids as well.  The Gradient
filter only works on image data.  This means that there is on gradient
filter for rectilinear grids and that any multiblock data set with mixed
data set types can't be used with the gradient filter either.  Because of
this I'm wondering why the Gradient of Unstructured DataSet filter was
limited to just vtkPointSets.  Obviously performance is an issue.  On an
image data with 100 million cells, 1000 by 1000 by 100 whole extent, it took
14.5 seconds to create the image data with the wavelet source and run the
Gradient filter.  Using the Gradient of Unstructured DataSet filter instead
it took 41.9 seconds.

The Gradient of Unstructured DataSet does have more functionality (operates
on arrays with more than a single component, can calculate vorticity,...)
but I'd like to look into getting a better interface to gradients and am
trying to encourage input on that process.

Thanks,
Andy
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