# How to set interpolation

**URL:** https://discourse.paraview.org/t/how-to-set-interpolation/12508
**Category:** ParaView Support
**Created:** [July 12, 2023, 3:34pm UTC](https://discourse.paraview.org/t/how-to-set-interpolation/12508 "2023-07-12T15:34:03Z")
**Posts on this page:** 7
**Page:** 1

<div class="post-metadata">

### Author: ![PetrKryslUCSD](https://discourse.paraview.org/user_avatar/discourse.paraview.org/petrkryslucsd/32/5908_2.png) [@PetrKryslUCSD](https://discourse.paraview.org/u/PetrKryslUCSD)
#### Post date: [July 12, 2023, 3:34pm UTC](https://discourse.paraview.org/t/how-to-set-interpolation/12508/1 "2023-07-12T15:34:03Z")

</div>

[Visualizing complex vibration modes - ParaView Support - ParaView](https://discourse.paraview.org/t/visualizing-complex-vibration-modes/6467)

The above thread suggested how to animate a complex field (harmonic vibration).

I wrote a bit of code to dump a Python script to animate the motion.  
Unfortunately, I am getting an error: `ValueError: 'Step' is not a valid value for Interpolation!`

I do want a Step interpolation, and I can get it through the dialogue in the animation view.  
But the code doesn’t work.

Any idea what is wrong with the setup of the key frames?

```auto
from paraview.simple import *
paraview.simple._DisableFirstRenderCameraReset()
renderView1 = GetActiveViewOrCreate('RenderView')

# find source: pick up the name from the Julia source
shape_source = FindSource('shape_2.97094e+02.vtu')

# create a new 'Programmable Filter'
programmableFilter1 = ProgrammableFilter(Input=shape_source)
programmableFilter1.Script = ''
programmableFilter1.RequestInformationScript = ''
programmableFilter1.RequestUpdateExtentScript = ''
programmableFilter1.PythonPath = ''

# Properties modified on programmableFilter1
programmableFilter1.Script = ''
programmableFilter1.RequestInformationScript = ''
programmableFilter1.RequestUpdateExtentScript = ''
programmableFilter1.PythonPath = ''

# get active view
renderView1 = GetActiveViewOrCreate('RenderView')
# uncomment following to set a specific view size
# renderView1.ViewSize = [1492, 589]

# get layout
layout1 = GetLayout()

# show data in view
programmableFilter1Display = Show(programmableFilter1, renderView1, 'UnstructuredGridRepresentation')

# trace defaults for the display properties.
programmableFilter1Display.Representation = 'Surface'
programmableFilter1Display.ColorArrayName = [None, '']
programmableFilter1Display.OSPRayScaleFunction = 'PiecewiseFunction'
programmableFilter1Display.SelectOrientationVectors = 'None'
programmableFilter1Display.ScaleFactor = 0.1273491016886233
programmableFilter1Display.SelectScaleArray = 'None'
programmableFilter1Display.GlyphType = 'Arrow'
programmableFilter1Display.GlyphTableIndexArray = 'None'
programmableFilter1Display.GaussianRadius = 0.0063674550844311645
programmableFilter1Display.SetScaleArray = [None, '']
programmableFilter1Display.ScaleTransferFunction = 'PiecewiseFunction'
programmableFilter1Display.OpacityArray = [None, '']
programmableFilter1Display.OpacityTransferFunction = 'PiecewiseFunction'
programmableFilter1Display.DataAxesGrid = 'GridAxesRepresentation'
programmableFilter1Display.PolarAxes = 'PolarAxesRepresentation'
programmableFilter1Display.ScalarOpacityUnitDistance = 0.054253560164564396

# hide data in view
Hide(shape_source, renderView1)

# update the view to ensure updated data information
renderView1.Update()

# Properties modified on programmableFilter1
programmableFilter1.Script = """
U_real = inputs[0].PointData['U_real']
U_imag = inputs[0].PointData['U_imag']

executive = self.GetExecutive()
time_value = executive.GetOutputInformation(0).Get(executive.UPDATE_TIME_STEP())

U = (U_real * cos(2*pi*time_value) - U_imag * sin(2*pi*time_value))

output.PointData.append(U, 'U')
"""

# update the view to ensure updated data information
renderView1.Update()

# Properties modified on programmableFilter1
programmableFilter1.RequestInformationScript = """
executive = self.GetExecutive()
outInfo = executive.GetOutputInformation(0)

outInfo.Remove(executive.TIME_STEPS())
for i in range(0, 400+1):
  outInfo.Append(executive.TIME_STEPS(), i/100)

outInfo.Remove(executive.TIME_RANGE())
outInfo.Append(executive.TIME_RANGE(), 0)
outInfo.Append(executive.TIME_RANGE(), 1)
"""

# get animation scene
animationScene1 = GetAnimationScene()

# get the time-keeper
timeKeeper1 = GetTimeKeeper()

# update animation scene based on data timesteps
animationScene1.UpdateAnimationUsingDataTimeSteps()

# create a new 'Warp By Vector'
warpByVector1 = WarpByVector(Input=programmableFilter1)
warpByVector1.Vectors = ['POINTS', 'U']

# show data in view
warpByVector1Display = Show(warpByVector1, renderView1, 'UnstructuredGridRepresentation')

# trace defaults for the display properties.
warpByVector1Display.Representation = 'Surface'
warpByVector1Display.ColorArrayName = [None, '']
warpByVector1Display.OSPRayScaleArray = 'U'
warpByVector1Display.OSPRayScaleFunction = 'PiecewiseFunction'
warpByVector1Display.SelectOrientationVectors = 'None'
warpByVector1Display.ScaleFactor = 0.12734916553420975
warpByVector1Display.SelectScaleArray = 'None'
warpByVector1Display.GlyphType = 'Arrow'
warpByVector1Display.GlyphTableIndexArray = 'None'
warpByVector1Display.GaussianRadius = 0.006367458276710487
warpByVector1Display.SetScaleArray = ['POINTS', 'U']
warpByVector1Display.ScaleTransferFunction = 'PiecewiseFunction'
warpByVector1Display.OpacityArray = ['POINTS', 'U']
warpByVector1Display.OpacityTransferFunction = 'PiecewiseFunction'
warpByVector1Display.DataAxesGrid = 'GridAxesRepresentation'
warpByVector1Display.PolarAxes = 'PolarAxesRepresentation'
warpByVector1Display.ScalarOpacityUnitDistance = 0.054253582666424625

# init the 'PiecewiseFunction' selected for 'ScaleTransferFunction'
warpByVector1Display.ScaleTransferFunction.Points = [-4.840145009488761e-06, 0.0, 0.5, 0.0, 3.06785751639229e-06, 1.0, 0.5, 0.0]

# init the 'PiecewiseFunction' selected for 'OpacityTransferFunction'
warpByVector1Display.OpacityTransferFunction.Points = [-4.840145009488761e-06, 0.0, 0.5, 0.0, 3.06785751639229e-06, 1.0, 0.5, 0.0]

# hide data in view
Hide(programmableFilter1, renderView1)

# update the view to ensure updated data information
renderView1.Update()

# Properties modified on warpByVector1
warpByVector1.ScaleFactor = 1.0

# update the view to ensure updated data information
renderView1.Update()

# get animation track
warpByVector1ScaleFactorTrack = GetAnimationTrack('ScaleFactor', index=0, proxy=warpByVector1)

# create keyframes for this animation track

# create a key frame
keyFrame9511 = CompositeKeyFrame()
keyFrame9511.KeyTime = 0.0
keyFrame9511.KeyValues = [1.33756e+03]
keyFrame9511.Interpolation = 'Step'
keyFrame9511.Base = 2.0
keyFrame9511.StartPower = 0.0
keyFrame9511.EndPower = 1.0
keyFrame9511.Phase = 0.0
keyFrame9511.Frequency = 1.0
keyFrame9511.Offset = 0.0

# create a key frame
keyFrame9512 = CompositeKeyFrame()
keyFrame9512.KeyTime = 1.0
keyFrame9512.KeyValues = [1.33756e+03]
keyFrame9512.Interpolation = 'Step'
keyFrame9512.Base = 2.0
keyFrame9512.StartPower = 0.0
keyFrame9512.EndPower = 1.0
keyFrame9512.Phase = 0.0
keyFrame9512.Frequency = 1.0
keyFrame9512.Offset = 0.0

# initialize the animation track
warpByVector1ScaleFactorTrack.KeyFrames = [keyFrame9511, keyFrame9512]

animationScene1.Play()

animationScene1.Play()

#### saving camera placements for all active views

# current camera placement for renderView1
renderView1.CameraPosition = [0.9397382619147922, -0.8500997386424357, -1.8495294823857338]
renderView1.CameraFocalPoint = [0.46404687523764426, 0.43327050958540075, 0.6787765407842903]
renderView1.CameraViewUp = [-0.1576136295811123, -0.8922072135678301, 0.42323070756715725]
renderView1.CameraParallelScale = 0.744106007631631

#### uncomment the following to render all views
# RenderAllViews()
# alternatively, if you want to write images, you can use SaveScreenshot(...).

```

---

<div class="post-metadata">

### Author: ![Kenneth\_Moreland](https://discourse.paraview.org/user_avatar/discourse.paraview.org/kenneth_moreland/32/15033_2.png) [@Kenneth\_Moreland](https://discourse.paraview.org/u/Kenneth_Moreland)
#### Post date: [July 12, 2023, 3:41pm UTC](https://discourse.paraview.org/t/how-to-set-interpolation/12508/2 "2023-07-12T15:41:41Z")

</div>

I don’t know much about the Python bindings for setting up animation, but when I run the trace I get a line like this:

```py
keyFrame9590.Interpolation = 'Boolean'

```

Perhaps you need to use `Boolean` instead of `Step`.

---

<div class="post-metadata">

### Author: ![PetrKryslUCSD](https://discourse.paraview.org/user_avatar/discourse.paraview.org/petrkryslucsd/32/5908_2.png) [@PetrKryslUCSD](https://discourse.paraview.org/u/PetrKryslUCSD)
#### Post date: [July 12, 2023, 3:51pm UTC](https://discourse.paraview.org/t/how-to-set-interpolation/12508/3 "2023-07-12T15:51:41Z")

</div>

Wow, it is Boolean. Weird… Before I had it set up as Ramp (and there is Ramp in the dialogue dropdown menu). Why is it that instead of Step!?

---

<div class="post-metadata">

### Author: ![PetrKryslUCSD](https://discourse.paraview.org/user_avatar/discourse.paraview.org/petrkryslucsd/32/5908_2.png) [@PetrKryslUCSD](https://discourse.paraview.org/u/PetrKryslUCSD)
#### Post date: [July 12, 2023, 4:02pm UTC](https://discourse.paraview.org/t/how-to-set-interpolation/12508/4 "2023-07-12T16:02:26Z")

</div>

You say you got it from the trace? For some reason trace does not work for me with that dialogue. I am on Windows, 5.11.0. I opened the Animation Keyframes dialog, changed things, stopped trace.  
There was nothing from that dialogue in the trace.

---

<div class="post-metadata">

### Author: ![Kenneth\_Moreland](https://discourse.paraview.org/user_avatar/discourse.paraview.org/kenneth_moreland/32/15033_2.png) [@Kenneth\_Moreland](https://discourse.paraview.org/u/Kenneth_Moreland)
#### Post date: [July 12, 2023, 5:23pm UTC](https://discourse.paraview.org/t/how-to-set-interpolation/12508/5 "2023-07-12T17:23:01Z")

</div>

> [@PetrKryslUCSD](#):
>
> Wow, it is Boolean. Weird… Before I had it set up as Ramp (and there is Ramp in the dialogue dropdown menu). Why is it that instead of Step!?

Yeah, weird. It looks like the underlying class to handle this is called [vtkPVBooleanKeyFrame](https://kitware.github.io/paraview-docs/latest/cxx/classvtkPVBooleanKeyFrame.html). I guess the original developer picked this name because it picks between two values. That must have been changed to `Step` in the GUI to be more clear, but the other name persists at the scripting level.

> [@PetrKryslUCSD](#):
>
> You say you got it from the trace? For some reason trace does not work for me with that dialogue. I am on Windows, 5.11.0. I opened the Animation Keyframes dialog, changed things, stopped trace.  
> There was nothing from that dialogue in the trace.

Playing around a bit, it looks like the interpolation and other parameters are not written to the traced script until you hit `OK` or `Apply` in the `Animation Keyframes` dialog box.

---

<div class="post-metadata">

### Author: ![PetrKryslUCSD](https://discourse.paraview.org/user_avatar/discourse.paraview.org/petrkryslucsd/32/5908_2.png) [@PetrKryslUCSD](https://discourse.paraview.org/u/PetrKryslUCSD)
#### Post date: [July 12, 2023, 5:25pm UTC](https://discourse.paraview.org/t/how-to-set-interpolation/12508/6 "2023-07-12T17:25:47Z")

</div>

No, I get nothing. I do click OK in the Animation Keyframes dialog, but there is nothing in the trace.

---

<div class="post-metadata">

### Author: ![Kenneth\_Moreland](https://discourse.paraview.org/user_avatar/discourse.paraview.org/kenneth_moreland/32/15033_2.png) [@Kenneth\_Moreland](https://discourse.paraview.org/u/Kenneth_Moreland)
#### Post date: [July 12, 2023, 5:43pm UTC](https://discourse.paraview.org/t/how-to-set-interpolation/12508/7 "2023-07-12T17:43:51Z")

</div>

¯\(°\_o)/¯

I tried with ParaView 5.11.0 and the trace works fine. I’m on a Mac, but I don’t know why that would make a difference.

Maybe someone else could try.