[Paraview] Failed to determine the LookupTable being used

[Sgouros, Thomas]

Hello all:

I have a trace from a simple contour that I drew on a data set, and there
are parts of it that I don't understand. Here it is, with some question
numbers:

from paraview.simple import *

data = EnSightReader(CaseFileName='/my/data/file.case')

renderView1 = GetActiveViewOrCreate('RenderView')
dataDisplay = Show(data, renderView1)    ## 1

dataDisplay.Representation = 'Surface'
renderView1.ResetCamera()
dataDisplay.SetScalarBarVisibility(renderView1, True)
renderView1.Update()

pressureLUT = GetColorTransferFunction('pressure')  ## 2
contour1 = Contour(Input=data)

contour1.ContourBy = ['POINTS', 'uds_0_scalar']
contour1.Isosurfaces = [500.0]

contour1Display = Show(contour1, renderView1)
contour1Display.Representation = 'Surface'
Hide(data, renderView1)

contour1Display.SetScalarBarVisibility(renderView1, True) ## 3
renderView1.Update()


My questions:

 1. Why do I have to "Show" the raw data right after it's read? I almost
never actually want to do that. I just want to show the contour. Showing
and Hiding the raw data seems like a waste of cycles, but when I remove
references to dataDisplay, I get an error: "Failed to determine the
LookupTable being used." which seems oddly unrelated to what I did.

 2. Where does this value get used? It doesn't seem to me that it is being
used, but it seems related to the last and the next question:

 3. When I choose different scalar values to contour, I often see the
same "Failed to determine the LookupTable being used." here. There seem to
be some limitations on what scalars I can use, but what are they and where
can I read more about these missing lookup tables?

Thank you,

 -Tom
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