discontinuousgridcreator.hh

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#pragma once
 
#include <cassert>
#include <cstdint>
#include <limits>
#include <vector>
 
#include <dune/common/exceptions.hh>
#include <dune/common/hybridutilities.hh>
#include <dune/grid/common/gridfactory.hh>
 
#include <dune/vtk/types.hh>
#include <dune/vtk/gridcreatorinterface.hh>
 
namespace Dune::Vtk
{
  // Create a grid where the input points are not connected and the connectivity
  // describes separated elements.
  template <class Grid>
  struct DiscontinuousGridCreator
      : public GridCreatorInterface<Grid, DiscontinuousGridCreator<Grid>>
  {
    using Self = DiscontinuousGridCreator;
    using Super = GridCreatorInterface<Grid, DiscontinuousGridCreator>;
    using GlobalCoordinate = typename Super::GlobalCoordinate;
 
    struct CoordLess
    {
      template <class T, int N>
      bool operator() (FieldVector<T,N> const& lhs, FieldVector<T,N> const& rhs) const
      {
        for (int i = 0; i < N; ++i) {
          if (std::abs(lhs[i] - rhs[i]) < std::numeric_limits<T>::epsilon())
            continue;
          return lhs[i] < rhs[i];
        }
        return false;
      }
    };
 
    using Super::Super;
    using Super::factory;
 
    void insertVerticesImpl (std::vector<GlobalCoordinate> const& points,
                            std::vector<std::uint64_t> const& /*point_ids*/)
    {
      points_ = &points;
      uniquePoints_.clear();
      std::size_t idx = 0;
 
      for (auto const& p : points) {
        auto b = uniquePoints_.emplace(std::make_pair(p,idx));
        if (b.second) {
          factory().insertVertex(p);
          ++idx;
        }
      }
    }
 
    void insertElementsImpl (std::vector<std::uint8_t> const& types,
                            std::vector<std::int64_t> const& offsets,
                            std::vector<std::int64_t> const& connectivity)
    {
      assert(points_ != nullptr);
      std::size_t idx = 0;
      for (std::size_t i = 0; i < types.size(); ++i) {
        auto type = Vtk::to_geometry(types[i]);
        Vtk::CellType cellType{type};
 
        int nNodes = offsets[i] - (i == 0 ? 0 : offsets[i-1]);
        assert(nNodes > 0);
        std::vector<unsigned int> vtk_cell; vtk_cell.reserve(nNodes);
        for (int j = 0; j < nNodes; ++j) {
          std::size_t v_j = connectivity[idx++];
          std::size_t new_idx = uniquePoints_[(*points_)[v_j]];
          vtk_cell.push_back(new_idx);
        }
 
        if (cellType.noPermutation()) {
          factory().insertElement(type,vtk_cell);
        } else {
          // apply index permutation
          std::vector<unsigned int> cell(nNodes);
          for (int j = 0; j < nNodes; ++j)
            cell[j] = vtk_cell[cellType.permutation(j)];
          factory().insertElement(type,cell);
        }
      }
    }
 
  private:
    std::vector<GlobalCoordinate> const* points_ = nullptr;
    std::map<GlobalCoordinate, std::size_t, CoordLess> uniquePoints_;
  };
 
  // deduction guides
  template <class Grid>
  DiscontinuousGridCreator(GridFactory<Grid>&)
    -> DiscontinuousGridCreator<Grid>;
 
} // end namespace Dune::Vtk