[vtkusers] GetNumberOfPoints() returns 0

[Xiaobin Wang]

Hi users,

I have got a very wierd problem .
the code segment ---------------
   vtkSphereSource *Sphere= vtkSphereSource::New();
   Sphere->SetRadius(10);
   Sphere->SetCenter(0,0,0);
    vtkDoubleArray  *pDouble = vtkDoubleArray::New();
    N=Sphere->GetOutput()->GetNumberOfPoints();
    printf("%d,\n",N);

I expect N is a finite number of points of the polygonal data representing
the sphere.
But  i got N =0!
I really confused .can somebody help?
thanks for your time ...
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