Function ExtractSliceFromSeed

Filters/ParallelDIY2/vtkExtractSubsetWithSeed.cxx:196–311

}

std::vector<SeedT> ExtractSliceFromSeed(const vtkVector3d& seed,
  const std::vector<vtkVector3d>& dirs, BlockT* b, const diy::Master::ProxyWithLink&)
{
  auto sg = b->Input;
  assert(vtkStructuredData::GetDataDescriptionFromExtent(sg->GetExtent()) ==
    vtkStructuredData::VTK_STRUCTURED_XYZ_GRID);

  const vtkIdType cellid = b->CellLocator->FindCell(const_cast<double*>(seed.GetData()));
  if (cellid <= 0)
  {
    return std::vector<SeedT>();
  }

  // okay, we've determined that the seed lies in this block's grid. now we need to determine the
  // voi to extract based on the propagation directions provided.

  // using the cell's orientation, first determine which ijk axes the propagation directions
  // correspond to.
  auto cell_vectors = ::GetCellOrientationVectors(b->Input->GetCell(cellid));
  int propagation_mask[3] = { 0, 0, 0 };
  for (const auto& dir : dirs)
  {
    assert(dir.SquaredNorm() != 0);

    double max = 0.0;
    int axis = -1;
    for (int cc = 0; cc < 3; ++cc)
    {
      const auto dot = std::abs(dir.Dot(cell_vectors[cc]));
      if (dot > max)
      {
        max = dot;
        axis = cc;
      }
    }
    if (axis != -1)
    {
      propagation_mask[axis] = 1;
    }
  }
  assert(std::accumulate(propagation_mask, propagation_mask + 3, 0) < 3);

  int ijk[3];
  vtkStructuredData::ComputeCellStructuredCoordsForExtent(cellid, sg->GetExtent(), ijk);

  const auto voi = ComputeVOI(sg, ijk, propagation_mask);
  if (b->Regions.find(voi) != b->Regions.end())
  {
    return std::vector<SeedT>();
  }

  b->Regions.insert(voi);

  vtkVector<int, 6> cell_voi;
  vtkStructuredData::GetCellExtentFromPointExtent(voi.GetData(), cell_voi.GetData());

  std::vector<SeedT> next_seeds;
  for (int axis = 0; axis < 3; ++axis)