[vtkusers] Clipping PolyData after vtkPolyDataConnectivityFilter problem

[Alex Malyushytskyy]

I just want to add that clipping in my case supposed not to add any
new node, so it does not have to remove nodal arrays.

On Wed, Aug 10, 2011 at 9:05 PM, Alex Malyushytskyy
<alexmalvtk at gmail.com> wrote:
> I need to do the following manipulation with polydata:
> - split by connectivity
> - split by array values ( point and cell arrays )
> - do something to each part.
>
> Everything seems work, except splitting by array.
> The problem is that I am trying to achieve it
> with multiple clipping.
>
> But first clipping with vtkClipPolyData
> does not pass "RegionId" array  it gets from the input
> (vtkPolyDataConnectivityFilter output)
>
> Even though it does preserve cell data array which was added to poly
> data before connectivity filter.
>
> Questions is -  why point data array is not passed (with clipping ) to
> the vtkClipPolyData output?
> How to clip poly data properly limiting lower and upper of scalar
> without multiple filters?
>
> Code below demonstrates a problem by clipping output of
> vtkPolyDataConnectivityFilter.
>
> Before clip->Update();  there is 1 point array and 1 cell array,
> after clipping   there is no point array but there is 1 cell array,
>
> Regards,
>  Alex
>
>
> vtkAlgorithmOutput* inputConnection = .....
>
>
> vtkSmartPointer<vtkPolyDataConnectivityFilter> connectivityFilter =
> vtkSmartPointer<vtkPolyDataConnectivityFilter>::New();
> connectivityFilter->SetInputConnection( inputConnection  );
> connectivityFilter->SetExtractionModeToAllRegions();
> connectivityFilter->ColorRegionsOn ();
> connectivityFilter->Update();
>
> int regions = connectivityFilter->GetNumberOfExtractedRegions();
>
> if ( regions > 1 )
> {
>        vtkIndent indent( 1 );
>        connectivityFilter->GetOutput()->GetPointData()->SetActiveScalars(
> "RegionId" );
>        connectivityFilter->GetOutput()->PrintSelf(std::cout, indent);
>        qDebug() << "connectivityFilter cells = " <<
> connectivityFilter->GetOutput()->GetNumberOfCells()  << endl;
>
>        for ( int i=0; i < regions; i ++ )
>        {
>                qDebug() << "Before first clipping " << endl;
> //output = 1
>                qDebug() << "Number of PointData arrays: " <<
> connectivityFilter->GetOutput()->GetPointData()->GetNumberOfArrays()
> << endl;
> //output = 1
>                qDebug() << "Number of Cell data arrays: " <<
> connectivityFilter->GetOutput()->GetCellData()->GetNumberOfArrays() <<
> endl; // returns 1
>
>
>                vtkSmartPointer<vtkClipPolyData> clip =
> vtkSmartPointer<vtkClipPolyData>::New();
>                clip->SetInput( connectivityFilter->GetOutput() );
>                clip->InsideOutOff();
>                clip->SetValue( (float) i - 0.1 );
>                clip->Update();
>
>                qDebug() << "After first clipping vtkClipPolyData" << endl;
> //output = 0 // WHY?
>                qDebug() << "Number of PointData arrays: " <<
> clip->GetOutput()->GetPointData()->GetNumberOfArrays() << endl;
> //output = 1
>                qDebug() << "Number of Cell data arrays: " <<
> clip->GetOutput()->GetCellData()->GetNumberOfArrays() << endl;
>
>                qDebug() << "After first clipping connectivityFilter output" << endl;
> //output = 1
>                qDebug() << "Number of PointData arrays: " <<
> connectivityFilter->GetOutput()->GetPointData()->GetNumberOfArrays()
> << endl;
> //output = 1
>                qDebug() << "Number of Cell data arrays: " <<
> connectivityFilter->GetOutput()->GetCellData()->GetNumberOfArrays() <<
> endl;
>
>                vtkSmartPointer<vtkClipPolyData> clipInsideOut =
> vtkSmartPointer<vtkClipPolyData>::New();
>                clipInsideOut->SetInput(clip->GetOutput() );
>                clipInsideOut->InsideOutOn();
>
>                clipInsideOut->SetValue( (float) i + 0.1 );
>                clipInsideOut->Update();
>                clipInsideOut->GetOutput()->PrintSelf(std::cout, indent);
>
> ....................
>
>        }
>
>
>
> }
>