[vtkusers] Traversing vtkPolyData returns incorrect number of points

[Dan Lipsa]

Hi David,
You have shared points between cells so it is normal you'll get a bigger
number when you count all the points from cells.

On Mon, May 23, 2016 at 10:01 AM, David Edmunds <David.Edmunds at icr.ac.uk>
wrote:

> Dear all,
>
> I am traversing a vtkPolyData object which is read in from a file using
> vtkXMLPolyDataReader. I access the number of points in the vtkPolyData in
> two different ways, here is my source code:
>
>   vtkSmartPointer<vtkXMLPolyDataReader> reader =
> vtkSmartPointer<vtkXMLPolyDataReader>::New();
>   reader->SetFileName("/Users/dedmunds/Desktop/organ_Body.vtp");
>   reader->Update();
>   vtkSmartPointer<vtkPolyData> poly_data = reader->GetOutput();
>
>   cout << "Number of points: " << poly_data->GetNumberOfPoints() << endl;
>
>   int traversal_points = 0;
>   for (int i=0; i<poly_data->GetNumberOfCells(); i++) {
>     traversal_points += poly_data->GetCell(i)->GetNumberOfPoints();
>   }
>   cout << "Traversal number of points: " << traversal_points << endl;
>
> Here is the output:
>
> Number of points: 286402
> Traversal number of points: 143204
>
> Why do I get two different answers? The second number is approximately
> half the first. What am I doing wrong?
>
> Thanks for your help,
>
> Kind regards,
>
> Dave
>
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