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

[Mathieu Westphal]

Du you inherit from vtkPolydataAlgorithm ? You should inherit from
vtkAlgorithm .
 On 14 Jul 2015 23:40, "houssen" <houssen at ipgp.fr> wrote:

> 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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