[vtkusers] Traversing vtkPolyData returns incorrect number of points

[David Edmunds]

Hi Dan,

Thanks, but I actually get a much smaller number when I count all the points from cells. Also, in my input dataset the cells are disjoint, i.e. no points are shared between multiple cells.

Kind regards,

Dave

On 23 May 2016, at 16:51, Dan Lipsa <dan.lipsa at kitware.com<mailto:dan.lipsa at kitware.com>> wrote:

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<mailto: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

The Institute of Cancer Research: Royal Cancer Hospital, a charitable Company Limited by Guarantee, Registered in England under Company No. 534147 with its Registered Office at 123 Old Brompton Road, London SW7 3RP.

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The Institute of Cancer Research: Royal Cancer Hospital, a charitable Company Limited by Guarantee, Registered in England under Company No. 534147 with its Registered Office at 123 Old Brompton Road, London SW7 3RP.

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