Function CleanOutputPoints

Filters/Modeling/vtkContourLoopExtraction.cxx:244–290

Discard unused points; renumber output polylines and polygons. Performs this operation in place.

// Discard unused points; renumber output polylines and polygons.
// Performs this operation in place.
void CleanOutputPoints(vtkPolyData* output)
{
  // Mark points used by lines or polygons, and create a point map
  // of old point ids to new point ids.
  vtkIdType numPts = output->GetNumberOfPoints();
  std::vector<vtkIdType> ptMap(numPts, 0);
  vtkPoints* pts = output->GetPoints();

  // Get the connectivity of the lines and polygons. Run through them
  // and mark points that are used.
  vtkCellArray* lines = output->GetLines();
  vtkIdType numLinesIds = lines->GetNumberOfConnectivityIds();
  if (numLinesIds > 0)
  {
    MarkPointUses(lines, numLinesIds, ptMap);
  }

  vtkCellArray* polys = output->GetPolys();
  vtkIdType numPolysIds = polys->GetNumberOfConnectivityIds();
  if (numPolysIds > 0)
  {
    MarkPointUses(polys, numPolysIds, ptMap);
  }

  // Renumber points / build the point map
  vtkNew<vtkPoints> newPts;
  vtkIdType newId;
  for (auto pId = 0; pId < numPts; ++pId)
  {
    if (ptMap[pId] != 0)
    {
      newId = newPts->InsertNextPoint(pts->GetPoint(pId));
      ptMap[pId] = newId;
    }
  }
  output->SetPoints(newPts);

  // Update the point ids (in place).
  if (numLinesIds > 0)
  {
    UpdatePointUses(lines, numLinesIds, ptMap);
  }
  if (numPolysIds > 0)
  {
    UpdatePointUses(polys, numPolysIds, ptMap);
  }
} // CleanOutputPoints

} // anonymous namespace