[Paraview-developers] Where does the vtkSelection come from?

[Utkarsh Ayachit]

Cornelis,

Several of the hints are documented on the doxygen pages:
http://www.paraview.org/ParaView3/Doc/Nightly/www/cxx-doc/index.html

On Wed, Jan 18, 2017 at 7:29 AM, Cornelis Bockemühl
<cornelis.bockemuehl at gmail.com> wrote:
> Thanks Utkarsh,
>
> It looks like these were the final hints that made it happen for me!
>
> First the "hints" entry really did the "magic" I was looking for.
>
> And second I am using now a vtkPVSelectExtraction filter (inside my own
> filter) for converting all the different types of selection into all cell
> indices for easy further processing.
>
> Overall I am getting the impression that these "Hints" are covering still a
> lot more "magic" that is worth discovering... ;-)
>
> Regards,
> Cornelis
>
>
> 2017-01-17 23:03 GMT+01:00 Utkarsh Ayachit <utkarsh.ayachit at kitware.com>:
>>
>> The vtkSelection comes from a "Selection Source" proxy that ParaView
>> internally creates that defines the selection. sources.xml [1] defines
>> several types of selection sources, e.g. ThresholdSelectionSource,
>> IDSelectionSource, SelectionQuerySource.
>>
>> To make your filter behave like the "Extract Selection" filter where
>> it automatically sets up the selection, make sure you have the
>> <SelectionInput> hint [2].
>>
>> Utkarsh
>>
>> [1]
>> https://gitlab.kitware.com/paraview/paraview/blob/master/ParaViewCore/ServerManager/SMApplication/Resources/sources.xml#L1590-1904
>> [2]
>> https://gitlab.kitware.com/paraview/paraview/blob/master/ParaViewCore/ServerManager/SMApplication/Resources/filters.xml#L11911-11916
>>
>> On Tue, Jan 17, 2017 at 11:45 AM, Cornelis Bockemühl
>> <cornelis.bockemuehl at gmail.com> wrote:
>> > All day I am already struggling now with some possibly very "simple"
>> > problem: I am trying to write a filter that applies some operations only
>> > to
>> > selected cells of an "unstructured grid".
>> >
>> > I am taking the "extract selection" filter as an example. This filter
>> > takes
>> > the "data" stuff at input port 0 and a vtkSelection object at input port
>> > 1,
>> > then does the proper processing. However, from a user perspective the
>> > filter
>> > is attached to one single input data set with selections. Like exactly
>> > the
>> > unstructured grid with some cells selected: I can easily extract them
>> > with
>> > the "extract selection" filter - and I do not have to specify a second
>> > data
>> > item for input port 1!
>> >
>> > But if I am simulating exactly the code in the server XML (specifying
>> > two
>> > input ports, for "input" and "selection"), then copying all the relevant
>> > stuff from the cxx files of vtkPVExtractSelection.cxx,
>> > vtkExtractSelection.cxx and vtkExtractSelecitonBase.cxx - I do not get
>> > the
>> > same behaviour!
>> >
>> > Instead I am getting exactly what I would have expected otherwise: my
>> > filter
>> > asks for a second input data item - but what should I choose? And then
>> > it
>> > stops because indeed it does not find any vtkSelection data object at
>> > port
>> > 1.
>> >
>> > While the latter looks somehow logical to me I still wonder how the
>> > extract
>> > seleciton filter does the apparent "magic" of having that selection
>> > object
>> > at port 1 for further processing!
>> >
>> > Any hint where I should have a look into the code, or what else I might
>> > have
>> > forgotten?
>> >
>> > As I said I simulated the server XML and the cxx code, but now I guess
>> > that
>> > maybe there are still other places in the code where I should have a
>> > look??
>> >
>> > Thanks in advance for any helpful hints!
>> > Cornelis
>> >
>> > --
>> > Cornelis Bockemühl
>> > Basel, Schweiz
>> >
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>
>
>
>
> --
> Cornelis Bockemühl
> Basel, Schweiz