[vtkusers] SetScalar() removes my color scalars

[Doug Hoppes]

Ah…. Okay!  Thanks!  That’s extremely helpful.

From: vtkusers [mailto:vtkusers-bounces at vtk.org] On Behalf Of Cory Quammen
Sent: Thursday, March 03, 2016 9:56 AM
To: jhirsch
Cc: vtkusers at vtk.org
Subject: Re: [vtkusers] SetScalar() removes my color scalars

Doug,

This is a long-standing oddness in VTK. If you call SetScalars() on point data, for example, a side effect is that the current active scalars is removed from the point data! I have been bitten by this in the past. We should probably change this behavior to avoid surprising effects like this despite the backwards compatibility issues (which are hopefully few).

I recommend calling SetActiveScalars(const char* name) instead, which shouldn't remove your array.

HTH,
Cory


On Thu, Mar 3, 2016 at 8:09 AM, jhirsch <jan.hirsch at st.ovgu.de<mailto:jan.hirsch at st.ovgu.de>> wrote:
Hello Doug,
your source example just creates two arrays and set their names and
therefore has little to do with your problem, I guess. Can you copy more
lines of code that show the problem with the scalar replacement?

In general I would recommend to create a scalar array with 3 components and
use that for colours. Like this:

(that's from the example  here
<http://www.vtk.org/Wiki/VTK/Examples/Cxx/PolyData/ColoredPoints>  )




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Cory Quammen
R&D Engineer
Kitware, Inc.
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