[vtkusers] vtkPolyData

[Ahmed Mahmoud]

Hello All,
I have a 3D file I want to access the data attributes. I used this code(vtk
2.3 )

vtkPolyDataReader *reader=vtkPolyDataReader::New();
 reader->SetFileName (STUDY);
 reader->Update ();
 reader->GetOutput()->ReleaseDataFlagOn();
 vtkPolyData *poly =vtkPolyData ::New();
 poly = reader ->GetOutput ();
 vtkScalars * scalar=vtkScalars :: New();
 scalar = poly->GetPointData()->GetScalars();

but I found that scalar is NULL . What is the reason?
Thank you.
Ahmed