[Paraview] Algorithm causing reader RequestData when running

[Burlen Loring]

If I'm not mistaken, when creating a VTK pipeline inside of a PV filter, 
you need to make a shallow copy of the input dataset in order to keep 
the PV pipeline isolated as your VTK pipeline executes.

Try making a shallow copy of "input" and passing that into 
"extractBlockFilter", and see if it helps.

Burlen

Paul Edwards wrote:
> Hi,
>
> I am writing an algorithm to operate on a vtkMultiBlockDataSet where I
> would like to extract blocks depending on field data that is set.
> Internally in my algorithm I am using the vtkExtractBlock filter and
> when this is updated it causes the RequestData for my reader to be
> executed again.  This doesn't happen when applying ExtractBlock in
> ParaView.  Below I have included an example RequestData that causes
> the data to be reloaded (note: this only happens when running in
> parallel):
>
> 8<-----------------------------------------------------------------
> int vtkTestMulti::RequestData(
>         vtkInformation* vtkNotUsed(request),
>         vtkInformationVector** inputVector,
>         vtkInformationVector* outputVector)
> {
>
>     vtkInformation* inInfo = inputVector[0]->GetInformationObject(0);
>     vtkMultiBlockDataSet* input = vtkMultiBlockDataSet::SafeDownCast(
>             inInfo->Get(vtkDataObject::DATA_OBJECT()));
>
>     vtkInformation* outInfo = outputVector->GetInformationObject(0);
>     vtkMultiBlockDataSet* output = vtkMultiBlockDataSet::SafeDownCast(
>             outInfo->Get(vtkDataObject::DATA_OBJECT()));
>
>     VTK_CREATE(vtkExtractBlock, extractBlockFilter);
>     extractBlockFilter->SetInput(input);
>     extractBlockFilter->AddIndex(1);
>     extractBlockFilter->Update();
>     output->ShallowCopy(extractBlockFilter->GetOutput());
>
>     return 1;
> }
> ----------------------------------------------------------------->8
>
> Can anyone see what I am doing wrong or provide any pointers for where to look?
>
> Thanks in advance,
> Paul
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