[Paraview] choppy derivatives

[Peter Brady]

Hello list,

I have a 3D dataset with a Temperature field.  My goal is to insert a sphere
source and determine the tangential temperature gradient on the surface of
the sphere at various zenith angles.  The data is output from the code as
cell data.  Here is the way I'm doing this (through pvpython)

1.  Apply CellDataToPointData
2.  Apply ComputeDerivatives (to get the 'Scalar Gradient')
3.  Apply another CellDataToPointData (to turn the derivatives into point
data)
4.  Resample the data from step 3 with my sphere source.
5.  Use a programmable filter to combine the xyz derivatives appropriately.

The data is reasonable but it's fairly choppy.  When I look at dT/dx, dT/dy,
and dT/dz (before I project them onto the sphere surface), and plot them at
a particular zenith angle around the azimuth of the drop, dTdx and dTdy are
very smooth but dT/dz is fairly choppy (especially above the equator of the
drop).  If I expand my sphere to a place where there's not a lot going on
dT/dz seems to calm down.  Is there a way to smooth dT/dz in the location of
interest or should I try to write my own derivatives filter to make them
smoother?  Any thoughts?

Thanks,
Peter.
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