[ITK] [ITK-users] Problems with mesh I/O and conversions in ITK

[Carlos Henrique Villa Pinto]

Hi Matt and everyone,

So it seems the best thing to do is to convert the triangle strips to
another representation (supported by ITK) and then use
MeshFileReader/Writer normally, right?

I used VTK to do that, changing everything to polygons, and so
MeshFileReader/Writer were finally able to read and write the models
without data losses. Thank you very much for your help with that!

But there are still a problem: when I try to convert the resulting mesh to
a simplex mesh (using TriangleMeshToSimplexMeshFilter), my program seems to
enter an infinite loop. Trying to perform the same conversion in another
mesh (that one from the ITK example I mentioned earlier, which already uses
the polygon representation), everything works fine and my program executes
in just a few seconds. So perhaps there's something wrong in my triangle
strips -> polygons conversion.

Below is the source code for such conversion. I used VTK, so maybe this is
not the right place to ask, but any help would be greatly appreciated.

===========================================================================================================================
  // Read the input VTK polydata.

  vtkSmartPointer<vtkPolyDataReader> reader =
vtkSmartPointer<vtkPolyDataReader>::New();
  reader->SetFileName(inputFileName.c_str());
  reader->Update();

  std::cout << "PolyData read ok\n";

  // Convert the triangle strips to polygons.

  vtkSmartPointer<vtkPolyData> originalPoly = reader->GetOutput();

  vtkIdType    npts = 0;
  vtkIdType    *pts = NULL;
  vtkCellArray *strips = originalPoly->GetStrips();
  vtkCellArray *triangles = vtkCellArray::New();

  for (strips->InitTraversal(); strips->GetNextCell(npts, pts); )
    vtkTriangleStrip::DecomposeStrip(npts, pts, triangles);

  vtkSmartPointer<vtkPolyData> newPoly = vtkPolyData::New();
  newPoly->SetPoints(originalPoly->GetPoints());
  newPoly->SetPolys(triangles);
  newPoly->BuildLinks();
  triangles->Delete();

  std::cout << "TRIANGLE_STRIPS to POLYGONS conversion ok\n";

  // Write the output polydata.

  vtkSmartPointer<vtkPolyDataWriter> writer =
vtkSmartPointer<vtkPolyDataWriter>::New();
  writer->SetFileName(outputFileName.c_str());
  writer->SetInputData(newPoly);
  writer->Update();

  std::cout << "PolyData write ok\n";
===========================================================================================================================

Thanks,
[]s

​
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