the painter hierarchy to make those painters that don't really use polydata to
be subclasses of vtkPainter (they were made subclasses of vtkPolyDataPainter so
  that they could pass the polydata along the pipeline).

ENH: Added new vtkMultiGroupPolyDataMapper2 and vtkCompositePainter for
rendering composite datasets without using multiple mappers.
vtkMultiGroupPolyDataMapper2 will create a single display list for rendering all
blocks when display lists are enabled.