# No cell data from vtkThreshold in Python plugin (possible dup)

**URL:** https://discourse.paraview.org/t/no-cell-data-from-vtkthreshold-in-python-plugin-possible-dup/4168
**Category:** ParaView Support
**Tags:** vtk, python
**Created:** [April 24, 2020, 6:05am UTC](https://discourse.paraview.org/t/no-cell-data-from-vtkthreshold-in-python-plugin-possible-dup/4168 "2020-04-24T06:05:35Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![wsherman](https://discourse.paraview.org/letter_avatar_proxy/v4/letter/w/8797f3/32.png) [@wsherman](https://discourse.paraview.org/u/wsherman)
#### Post date: [April 24, 2020, 6:05am UTC](https://discourse.paraview.org/t/no-cell-data-from-vtkthreshold-in-python-plugin-possible-dup/4168/1 "2020-04-24T06:05:36Z")

</div>

_[I think I just deleted my post, so if not, this will be a duplicate posting. (I’m having quite a bit of difficulty with Discourse this evening – twice it thought I wanted to “abandon” my posting, and then lost the draft! Maybe 4th time is the charm.]_

I’m experimenting with a simple Python plugin that uses vtkThreshold but constrains the low and high values to a particular delta. The issue I’m having is that unlike the standard “Threshold” filter in ParaView, my simple plugin only outputs the `point` data, but not the `cell` data.

I think the most obvious consequence of this is that with the output from the ParaView built-in filter, I can render a Volume representation, whereas with my plugin, there is no option to render as a Volume.

I Googled around a bit, but wasn’t able to determine what the problem might be. One hypothesis I have is that the built-in filter may convert the point data to cell data after doing the processing.

Here’s my simple script, I used the Contour-Shrink example as my starting point, and I’ll add property parameters later, once I figure out my problem – or really once with the aid of the ParaView community, the problem is solved.

```auto
# Synchronized Threshold plugin (From ContourShrink example)
from vtkmodules.util.vtkAlgorithm import VTKPythonAlgorithmBase
from paraview.util.vtkAlgorithm import smproxy, smproperty, smdomain
import vtk # Note: added to ContourShrink example to make it work

@smproxy.filter(label="Threshold Sync")
@smproperty.input(name="Input")
@smdomain.datatype(dataTypes=["vtkDataSet"], composite_data_supported=False)
class ThresholdSync(VTKPythonAlgorithmBase):
  def __init__ (self):
      VTKPythonAlgorithmBase. __init__ (self)
      print "Loading Sync'd Threshold plugin"
  
  def RequestData(self, request, inInfo, outInfo):
      inp = vtk.vtkDataSet.GetData(inInfo[0])
      opt = vtk.vtkPolyData.GetData(outInfo)

      th = vtk.vtkThreshold()
      th.SetInputData(inp)
      print "number of point arrays " + str(inp.GetPointData().GetNumberOfArrays())
      print "number of cell arrays " + str(inp.GetCellData().GetNumberOfArrays())
      print "point data range: " + str(inp.GetPointData().GetArray(0).GetRange())
      th.ThresholdBetween(130.0, 150.0)
      th.Update() # Note: Update() not available in the Python Shell

      opt.ShallowCopy(th.GetOutput())
      return 1

```

I’m using the Wavelet source as the input with all default settings.

Thanks in advance, Bill