[Paraview] choppy derivatives

[Berk Geveci]

You have to get the leaf nodes of the multi-block dataset first. In
this case, I suspect inputBlock will be a leaf block.

-berk

On Thu, Apr 22, 2010 at 5:01 PM, Peter Brady <petertbrady at gmail.com> wrote:
> The location we're looking at is the interface between two fluids so there
> may be a discontinuity in the tangential derivatives for that reason.  I'm
> trying to write my own derivative and interpolation filters in a python
> programmable filter which will take  one-sided derivatives and use one-sided
> interpolation.  In order to do this I need to use cell data in my filter and
> not point data to avoid the interpolation that takes place.  Typically I
> access point data with something like:
>
>> input = self.GetInputDataObject(0, 0)
>> output = self.GetOutputDataObject(0)
>>
>> inputBlock = input.GetBlock(0)
>> # copy old data
>> output.CopyStructure(input)
>> outputBlock = inputBlock.NewInstance()
>> outputBlock.UnRegister(None)
>> outputBlock.CopyStructure(inputBlock)
>> output.SetBlock(0,outputBlock)
>>
>> # get number of points
>> numPts = input.GetNumberOfPoints()
>> # temperature gradient
>> GtArr = input.GetPointData().GetVectors('ScalarGradient')
>
> However, there doesn't seem to be an equivalent 'GetNumberOfCells()' or
> 'GetCellData()' for my multiblock data.  How can I access the cell data?
>
> Thanks for your help,
>
> Peter.
>
> On Tue, Mar 30, 2010 at 10:15 AM, Berk Geveci <berk.geveci at kitware.com>
> wrote:
>>
>> I wonder if this is because of the multiple celldata -> point data
>> conversions. Do you have an example dataset you can share?
>>
>> On Sun, Mar 28, 2010 at 1:45 AM, Peter Brady <petertbrady at gmail.com>
>> wrote:
>> > 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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