[Paraview-developers] How to implement an identity filter ?

Wed Jul 15 17:49:56 EDT 2015

Shawn, Joachim, thanks.
After a quick look at the code, if I got you right, on a 
REQUEST_DATA_OBJECT request, I still need to create a new instance of 
the input and to set it as the DATA_OBJECT of the vtkInfo of the output. 
I still have to test this, but, I got the idea !

Franck

Le 2015-07-15 15:47, Shawn Waldon a écrit :
> You might want to take a look at inheriting from
> vtkPassInputTypeAlgorithm[1] if you want the output type to be the
> same as the input type.  It already implements RequestDataObject the
> way that I think Joachim is suggesting.
>
> HTH,
> Shawn
>
> [1]:
> 
> http://www.vtk.org/doc/nightly/html/classvtkPassInputTypeAlgorithm.html
> [14]
>
> On Wed, Jul 15, 2015 at 7:27 AM, Joachim Pouderoux
> <joachim.pouderoux at kitware.com [15]> wrote:
>
>> Franck,
>>
>> You will have to override the RequestDataObject() method in order
>> to make your filter generic. This method is the one called to
>> generate the output data object.
>> Take a look at vtkGenerateIndexArray.cxx for instance, I think you
>> can just copy it in your class (which should be derivated from
>> vtkDataObjectAlgorithm).
>>
>> Best,
>>
>> JOACHIM POUDEROUX
>>
>>> _PhD, Technical Expert_
>>
>> 2015-07-15 11:57 GMT+02:00 houssen <houssen at ipgp.fr [9]>:
>>
>>> Seems that it is not possible to filter on vtkDataObject type.
>>> But with less generic types (like vtkUnstrucutredGrid for
>>> instance), the myFilter works : no error occur, but, viewpoint
>>> ends up to be empty. I get "zero" instead of "identity" : why ?!
>>>
>>> Franck
>>>
>>> Le 2015-07-14 23:38, houssen a écrit :
>>>
>>>> How to write an identity filter ? (1 input port, 1 output port,
>>>> output = input whatever input may be)
>>>>
>>>> I need to write a custom filter. I am used to VTK "from
>>>> outside"
>>>> (creating/handling vtk pipelines/scene/object from a main
>>>> program)
>>>> that is basically without the need to understand all internal
>>>> VTK
>>>> mechanics (except the SetInputConnection concept). I am not
>>>> yet used
>>>> to VTK internal mechanics that is necessary for writing a
>>>> ParaView
>>>> plugin.
>>>>
>>>> I need my filter to do "complex" stuffs. As I couldn't make it
>>>> work,
>>>> I simplified as much as possible to obtain finally an identity
>>>> filter
>>>> (!) : this is still not working. I feel I still miss something
>>>> from
>>>> VTK internal mechanics.
>>>>
>>>> As far as I understand, in the constructor, I need :
>>>> myFilter::myFilter () { SetNumberOfInputPorts  ( 1 );
>>>> SetNumberOfOutputPorts ( 1 ); }
>>>>
>>>> So then I need to implement the FillXXXPortInformation :
>>>> int myFilter::FillInputPortInformation ( int vtkNotUsed (
>>>> iPort ),
>>>> vtkInformation * ipInfo )
>>>> {
>>>>   if ( ipInfo ) ipInfo -> Set (
>>>> vtkAlgorithm::INPUT_REQUIRED_DATA_TYPE (), "vtkDataObject" );
>>>> //
>>>> Filter allowed data types
>>>>   return 1;
>>>> }
>>>> int myFilter::FillOutputPortInformation ( int vtkNotUsed (
>>>> iPort ),
>>>> vtkInformation * ipInfo )
>>>> {
>>>>   if ( ipInfo ) ipInfo -> Set ( vtkDataObject::DATA_TYPE_NAME
>>>> (),
>>>> "vtkDataObject" ); // Output data type to be created
>>>>   return 1;
>>>> }
>>>>
>>>> So, now I only need to implement the ProcessRequest gateway:
>>>> int myFilter::ProcessRequest ( vtkInformation * ipRequest,
>>>> vtkInformationVector ** ipInputVector, vtkInformationVector *
>>>> opOutputVector )
>>>> {
>>>>   if ( ipRequest && ipRequest -> Has (
>>>> vtkDemandDrivenPipeline::REQUEST_DATA () ) )
>>>>     if ( ipInputVector && opOutputVector ) opOutputVector =
>>>> ipInputVector[0];
>>>>    return Superclass::ProcessRequest ( ipRequest,
>>>> ipInputVector,
>>>> opOutputVector );
>>>> }
>>>>
>>>> I believed that I would be the only steps to proceed to get an
>>>> identity filter. When I use my identity filter in Paraview, I
>>>> get
>>>> errors like :
>>>> ERROR: In
>>>>
>>>>
>>>>
>>>
>>
> 
> /.../ParaView-v4.3.1-source/VTK/Common/ExecutionModel/vtkDemandDrivenPipeline.cxx,
>>>> line 810
>>>> vtkPVPostFilterExecutive : Input for connection index 0 on
>>>> input port
>>>> index 0 for algorithm vtkPVPostFilter(0x16d0ec0) is of type
>>>> vtkDataObject, but a vtkPolyData is required.
>>>>
>>>> Some logic is still missing here : could somebody explain me
>>>> what and why ?
>>>>
>>>> Thanks,
>>>>
>>>> Franck
>>>>
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