Method ExtractSelectedCells

Filters/Extraction/vtkExtractSelection.cxx:896–966

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//------------------------------------------------------------------------------
void vtkExtractSelection::ExtractSelectedCells(
  vtkDataSet* input, vtkUnstructuredGrid* output, vtkSignedCharArray* cellInside, bool extractAll)
{
  vtkLogScopeF(TRACE, "ExtractSelectedCells");
  const vtkIdType numPts = input->GetNumberOfPoints();
  const vtkIdType numCells = input->GetNumberOfCells();

  // The "input" is a shallow copy of the input to this filter and hence we can
  // modify it. We add original cell ids and point ids arrays.
  vtkNew<vtkIdTypeArray> originalPointIds;
  originalPointIds->SetNumberOfComponents(1);
  originalPointIds->SetName("vtkOriginalPointIds");
  originalPointIds->SetNumberOfTuples(numPts);
  vtkSMPTools::For(0, numPts,
    [&](vtkIdType begin, vtkIdType end)
    {
      for (vtkIdType ptId = begin; ptId < end; ++ptId)
      {
        originalPointIds->SetValue(ptId, ptId);
      }
    });
  input->GetPointData()->AddArray(originalPointIds);

  vtkNew<vtkIdTypeArray> originalCellIds;
  originalCellIds->SetNumberOfComponents(1);
  originalCellIds->SetName("vtkOriginalCellIds");
  originalCellIds->SetNumberOfTuples(numCells);
  vtkSMPTools::For(0, numCells,
    [&](vtkIdType begin, vtkIdType end)
    {
      for (vtkIdType cellId = begin; cellId < end; ++cellId)
      {
        originalCellIds->SetValue(cellId, cellId);
      }
    });
  input->GetCellData()->AddArray(originalCellIds);

  vtkNew<vtkExtractCells> extractor;
  extractor->SetContainerAlgorithm(this);
  if (extractAll)
  {
    // all elements are selected, pass all data.
    // we still use the extractor since it does the data conversion, if needed
    extractor->SetExtractAllCells(true);
  }
  else
  {
    // convert insideness array to cell ids to extract.
    vtkNew<vtkIdList> ids;
    ids->Allocate(numCells);
    vtkUnsignedCharArray* ghostArray = input->GetCellGhostArray();
    for (vtkIdType cc = 0; cc < numCells; ++cc)
    {
      if (ghostArray && ghostArray->GetValue(cc) == vtkDataSetAttributes::HIDDENCELL)
      {
        // skip this cell
        continue;
      }