How to get vtkDataSet (cells, points, ...) information from a source in VTK-9?

Support
3

Thanks!
I’m misunderstanding something though.
I’ve subclassed vtkAbstractPolyDataReader to TopoGridReader, which includes these members:

    /// Grid points
    vtkSmartPointer<vtkPoints> gridPoints_;

    /// Delaunay triangle vertices
    vtkSmartPointer<vtkCellArray> gridPolygons_;

My TopoGridReader::RequestData() looks like:

int TopoGridReader::RequestData(vtkInformation* request,
			       vtkInformationVector** inputVector,
			       vtkInformationVector* outputVector) {
  
  vtkInformation* outInfo = outputVector->GetInformationObject(0);
  vtkDataSet* output = vtkDataSet::GetData(outInfo);
 
  vtkPolyData* polyOutput = vtkPolyData::SafeDownCast(output);
  [... populate gridPoints_ and gridPolygons_ …]

  // Save to output points and polygons
  polyOutput->SetPoints(gridPoints_);
  polyOutput->SetPolys(gridPolygons_);

Then when building the pipeline, data from TopoGridReader is rendered as I expect it, but TopoGridReader::GetOutput() seems to indicate 0 points and 0 cells:

gridReader->SetFileName(filename);
gridReader->Update();  // Invokes gridReader->RequestData()

/// DEBUG ////
vtkDataSet* dataset = gridReader_->GetOutput();

vtkCellData* cellData = dataset->GetCellData();
// How many cells in dataset?
qDebug() << "#cells: " << cellData->GetNumberOfArrays();
    
vtkPointData *pointData = dataset->GetPointData();
// How many points in dataset?
qDebug() << "#points: " << pointData->GetNumberOfArrays();

The debug output shows 0 cells and 0 points. What am I doing wrong here?

#cells:  0
#points:  0

Thanks!