[vtkusers] Use transfer function editors from Python?

[Cory Quammen]

On Fri, Apr 15, 2016 at 11:46 AM, Elvis Stansvik
<elvis.stansvik at orexplore.com> wrote:
> 2016-04-15 16:36 GMT+02:00 Elvis Stansvik <elvis.stansvik at orexplore.com>:
>>
>> 2016-04-15 16:09 GMT+02:00 Cory Quammen <cory.quammen at kitware.com>:
>>>
>>> Hi Elvis,
>>>
>>> Have a look at
>>>
>>>
>>> http://www.vtk.org/gitweb?p=VTK.git;a=blob;f=Charts/Core/Testing/Cxx/TestScalarsToColors.cxx
>>>
>>> for an example of how to set up the transfer function editors used in
>>> ParaView.
>>>
>>> You can eliminate the check at the end for vtkOpenGL2ContextDevice2D -
>>> make sure to initialize and start the interactor, though.
>>>
>>> I don't see anything in this example that won't work in Python - if
>>> there is, please report back any problems you encounter.
>>
>>
>> Excellent, thanks a lot. I'll report back how it went.
>
>
> Worked like a charm :) It's not quite the same as the editors in ParaView
> though. In ParaView, the opacity and color transfer functions are edited
> separately, like this:
>
>     https://blog.kitware.com/blog/files/48_1536770536.png
>
> Do you know if it's possible to get that kind of editing through VTK
> classes, with the color transfer function edited using a gradient editor
> below and the X/Y editor only for the the opacity transfer function, or is
> ParaView doing something custom here?

Yes. You can use a vtkPiecewiseFunctionItem and
vtkPiecewiseControlePointsItem to edit the opacity function and a
vtkColorTransferFunctionItem and a vtkColorTransferControlPointsItem
to edit the color transfer function. These can be displayed in two
separate widgets, much like ParaView does. In each widget, you can
have a vtkContextView. This is probably the easiest implementation for
what you are after.

Cory

> (I the class vtkCompositeTransferFunctionItem has "composite" in its name
> precisely because it provides editing of both color/opacity in the same
> editor, while I would like the separated approach that ParaView has.)
>
> Elvis
>
>>
>> Elvis
>>
>>>
>>>
>>> HTH,
>>> Cory
>>>
>>> On Fri, Apr 15, 2016 at 8:54 AM, Elvis Stansvik
>>> <elvis.stansvik at orexplore.com> wrote:
>>> > Hi all,
>>> >
>>> > I'd like to use the transfer function editors that VTK seems to provide
>>> > (used by e.g. Paraview) from Python. Is it possible?
>>> >
>>> > Looking at
>>> >
>>> >    http://www.vtk.org/pipermail/vtkusers/2013-December/082410.html
>>> >
>>> > I read the slightly worrying:
>>> >
>>> >     "[...] Save/restore state and python interface are not working as
>>> > expected. [...]"
>>> >
>>> > Though that was an old message when the new editors were first
>>> > introduced in
>>> > 2013. Is it still the case that the Python interface for the editor
>>> > classes
>>> > is not working as expected?
>>> >
>>> > Does anyone know of a Python application/example that makes use of the
>>> > editors? (I'm using VTK 6.2 and PyQt 5.5.1).
>>> >
>>> > Thanks,
>>> > Elvis
>>> >
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>>>
>>>
>>>
>>> --
>>> Cory Quammen
>>> R&D Engineer
>>> Kitware, Inc.
>>
>>
>



-- 
Cory Quammen
R&D Engineer
Kitware, Inc.