# vtkAngularPeriodicFilter vtkCutter 2

**URL:** https://discourse.paraview.org/t/vtkangularperiodicfilter-vtkcutter-2/11532
**Category:** ParaView Support
**Tags:** vtk, python
**Created:** [February 28, 2023, 12:37pm UTC](https://discourse.paraview.org/t/vtkangularperiodicfilter-vtkcutter-2/11532 "2023-02-28T12:37:57Z")
**Posts on this page:** 2
**Page:** 1

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### Author: ![Rigel](https://discourse.paraview.org/letter_avatar_proxy/v4/letter/r/8e7dd6/32.png) [@Rigel](https://discourse.paraview.org/u/Rigel)
#### Post date: [February 28, 2023, 12:37pm UTC](https://discourse.paraview.org/t/vtkangularperiodicfilter-vtkcutter-2/11532/1 "2023-02-28T12:37:57Z")

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Hi,

I have a 3D VTK dataset (on the form of a 45° wedge) and I want to post-process it in a Python script (using `pvbatch`). I apply the following filters:

```auto
# Apply angular periodic filter
print("\tApplying angular periodic filter")
data = vtkutils.angularPeriodic_vtk(data, 45., 2, [0., 0., 0.])
print(data.GetOutput())

# Slice through data
print("\tSlicing")
data = vtkutils.cut_vtk(data, cut)
print(data.GetOutput())

```

Here is the definition of the functions used above:

```auto
def angularPeriodic_vtk(data, rotationAngle, rotationAxis, center):
    angularPeriodic = vtk.vtkAngularPeriodicFilter()
    angularPeriodic.SetInputConnection(data.GetOutputPort())
    angularPeriodic.SetRotationAngle(rotationAngle)
    angularPeriodic.SetRotationAxis(rotationAxis)
    angularPeriodic.SetCenter(center)
    angularPeriodic.SetComputeRotationsOnTheFly(False)
    angularPeriodic.Update()
    return angularPeriodic

def cut_vtk(data,plane):
    cutter = vtk.vtkCutter()
    cutter.SetCutFunction(plane)
    cutter.SetInputConnection(data.GetOutputPort())
    cutter.Update()
    return cutter

```

The output from `angularPeriodic_vtk` seems fine (a `vtkMultiBlockDataSet` comprised of 8 children), but the output from `cut_vtk` is just `None` (i.e. all data arrays are gone)… Could you help me figure out what is going on?

Thanks a lot,

---

<div class="post-metadata">

### Author: ![carwischma](https://discourse.paraview.org/letter_avatar_proxy/v4/letter/c/46a35a/32.png) [@carwischma](https://discourse.paraview.org/u/carwischma)
#### Post date: [March 12, 2023, 12:50pm UTC](https://discourse.paraview.org/t/vtkangularperiodicfilter-vtkcutter-2/11532/2 "2023-03-12T12:50:13Z")

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Hi Rigel,

a similar problem is described in [https://discourse.vtk.org/t/vtkthreshold-not-working-with-vtkmultiblockdataset/5406](https://discourse.vtk.org/t/vtkthreshold-not-working-with-vtkmultiblockdataset/5406) - It obviously has to do with the `GetOuput()` method supposed to serve a `vtkUnstructuredGrid`. I managed to access the cut `vtkMultiBlockDataSet` by using the method `cutter.GetOutputDataObject(0)`