Function StructuredExecuteWithBlanking

Filters/Geometry/vtkDataSetSurfaceFilter.cxx:87–282

 */
template <typename DataSetT>
bool StructuredExecuteWithBlanking(
  DataSetT* input, vtkPolyData* output, vtkDataSetSurfaceFilter* self)
{
  if (input == nullptr)
  {
    return false;
  }

  int inExtent[6];
  input->GetExtent(inExtent);
  if (vtkStructuredData::GetDataDimension(inExtent) != 3 || !input->HasAnyBlankCells())
  {
    // no need to use this logic for non 3D cells or if no blanking is provided.
    return false;
  }

  vtkLogScopeF(TRACE, "StructuredExecuteWithBlanking (fastMode=%d)", (int)self->GetFastMode());
  vtkNew<vtkPoints> points;
  points->Allocate(input->GetNumberOfPoints() / 2);
  output->AllocateEstimate(input->GetNumberOfCells(), 4);
  output->SetPoints(points);

  // Extracts a either the min (or max) face along the `axis` for the cell
  // identified by `cellId` in the input dataset.
  auto getFace = [&inExtent](const int ijk[3], const int axis, bool minFace)
  {
    const int iAxis = (axis + 1) % 3;
    const int jAxis = (axis + 2) % 3;

    int ptIjk[3] = { ijk[0], ijk[1], ijk[2] };
    if (!minFace)
    {
      ++ptIjk[axis];
    }

    std::array<vtkIdType, 4> face;
    face[0] = vtkStructuredData::ComputePointIdForExtent(inExtent, ptIjk);

    ++ptIjk[iAxis];
    face[1] = vtkStructuredData::ComputePointIdForExtent(inExtent, ptIjk);

    ++ptIjk[jAxis];
    face[2] = vtkStructuredData::ComputePointIdForExtent(inExtent, ptIjk);

    --ptIjk[iAxis];
    face[3] = vtkStructuredData::ComputePointIdForExtent(inExtent, ptIjk);

    if (minFace)
    {
      // invert face order to get an outside pointing normal.
      return std::array<vtkIdType, 4>({ face[0], face[3], face[2], face[1] });
    }

    return face;
  };

  // Passes data arrays. Also adds `originalIds` the output if `arrayName`
  // non-null.