Filter to Data newbie question

[Dmitry Brodsky]

Hi,

How does one obtain data from a filter, or make the filter execute
such that a concrete object is instantiated and data can be obtained.

I have the output from vtkContourFilter and I would like to retrieve all
the vertices and polygons.  I have tried to do

vtkPolyData *pd = contourfilter->GetOutput( );

and then 

vtkCellArray *verts = pd->GetVerts( );
cerr << verts->GetNumberOfCells( ) << endl;
vtkCellArray *polys = pd->GetPolys( );
cerr << polys->GetNumberOfCells( ) << endl;

But the number of verts and polys is always zero.

Thanks for any help
ttyl
Dima

-- 
Dima Brodsky                                   dima at cs.ubc.ca
201-2366 Main Mall                             (604) 822-6179 (Office)
Department of Computer Science                 (604) 822-2895 (DSG Lab)
University of British Columbia, Canada         (604) 822-5485 (FAX)

Computers are like Old Testament gods; lots of rules and no mercy.
							  (Joseph Campbell)
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