[vtkusers] Selections: cells vs points

[David Doria]

When I use this (http://vtk.org/Wiki/VTK/Examples/ExtractSelection):

  vtkSmartPointer<vtkSelectionNode> selectionNode =
      vtkSmartPointer<vtkSelectionNode>::New();
  selectionNode->SetFieldType(vtkSelectionNode::POINT);
  selectionNode->SetContentType(vtkSelectionNode::INDICES);
  selectionNode->SetSelectionList(ids);

with the vtkExtractSelection filter, it seems to extract points AND
cells (I was expecting just points).

When I use this (http://vtk.org/Wiki/VTK/Examples/ExtractSelectionCells):
  vtkSmartPointer<vtkSelectionNode> selectionNode =
      vtkSmartPointer<vtkSelectionNode>::New();
  selectionNode->SetFieldType(vtkSelectionNode::CELL);
  selectionNode->SetContentType(vtkSelectionNode::INDICES);
  selectionNode->SetSelectionList(ids);

It seems to extract nothing.

Can anyone explain this behavior?

Thanks,

David