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

[Joachim Pouderoux]

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*
*Kitware SAS <http://www.kitware.fr>*


2015-07-15 11:57 GMT+02:00 houssen <houssen at ipgp.fr>:

> 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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>
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