gmshwriter.hh

// SPDX-FileCopyrightText: Copyright © DUNE Project contributors, see file LICENSE.md in module root
// SPDX-License-Identifier: LicenseRef-GPL-2.0-only-with-DUNE-exception
// -*- tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
// vi: set et ts=4 sw=2 sts=2:
#ifndef DUNE_GRID_IO_FILE_GMSHWRITER_HH
#define DUNE_GRID_IO_FILE_GMSHWRITER_HH
 
#include <fstream>
#include <iostream>
#include <iomanip>
#include <string>
#include <vector>
 
#include <dune/common/exceptions.hh>
#include <dune/geometry/type.hh>
#include <dune/geometry/referenceelements.hh>
#include <dune/grid/common/grid.hh>
#include <dune/grid/common/mcmgmapper.hh>
 
namespace Dune {
 
  template <class GridView>
  class GmshWriter
  {
  private:
    const GridView gv;
    int precision;
 
    static const unsigned int dim = GridView::dimension;
    static const unsigned int dimWorld = GridView::dimensionworld;
    static_assert( (dimWorld <= 3), "GmshWriter requires dimWorld <= 3." );
 
    template<typename Entity>
    std::size_t nodeIndexFromEntity(const Entity& entity, int i) const {
      return gv.indexSet().subIndex(entity, i, dim)+1;
    }
 
    static std::size_t translateDuneToGmshType(const GeometryType& type) {
      std::size_t element_type;
 
      if (type.isLine())
        element_type = 1;
      else if (type.isTriangle())
        element_type = 2;
      else if (type.isQuadrilateral())
        element_type = 3;
      else if (type.isTetrahedron())
        element_type = 4;
      else if (type.isHexahedron())
        element_type = 5;
      else if (type.isPrism())
        element_type = 6;
      else if (type.isPyramid())
        element_type = 7;
      else if (type.isVertex())
        element_type = 15;
      else
        DUNE_THROW(Dune::IOError, "GeometryType " << type << " is not supported by gmsh.");
 
      return element_type;
    }
 
    void outputElements(std::ofstream& file, const std::vector<int>& physicalEntities, const std::vector<int>& physicalBoundaries) const {
      MultipleCodimMultipleGeomTypeMapper<GridView> elementMapper(gv, mcmgElementLayout());
      std::size_t counter(1);
      for (const auto& entity : elements(gv)) {
        // Check whether the type is compatible. If not, close file and rethrow exception.
        try {
          std::size_t element_type = translateDuneToGmshType(entity.type());
 
          file << counter << " " << element_type;
          // If present, set the first tag to the physical entity
          if (!physicalEntities.empty())
            file << " " << 1 << " " << physicalEntities[elementMapper.index(entity)];
          else
            file << " " << 0; // "0" for "I do not use any tags."
 
          // Output list of nodes.
          // 3, 5 and 7 got different vertex numbering compared to Dune
          if (3 == element_type)
            file << " "
                 << nodeIndexFromEntity(entity, 0) << " " << nodeIndexFromEntity(entity, 1) << " "
                 << nodeIndexFromEntity(entity, 3) << " " << nodeIndexFromEntity(entity, 2);
          else if (5 == element_type)
            file << " "
                 << nodeIndexFromEntity(entity, 0) << " " << nodeIndexFromEntity(entity, 1) << " "
                 << nodeIndexFromEntity(entity, 3) << " " << nodeIndexFromEntity(entity, 2) << " "
                 << nodeIndexFromEntity(entity, 4) << " " << nodeIndexFromEntity(entity, 5) << " "
                 << nodeIndexFromEntity(entity, 7) << " " << nodeIndexFromEntity(entity, 6);
          else if (7 == element_type)
            file << " "
                 << nodeIndexFromEntity(entity, 0) << " " << nodeIndexFromEntity(entity, 1) << " "
                 << nodeIndexFromEntity(entity, 3) << " " << nodeIndexFromEntity(entity, 2) << " "
                 << nodeIndexFromEntity(entity, 4);
          else {
            for (int k = 0; k < entity.geometry().corners(); ++k)
              file << " " << nodeIndexFromEntity(entity, k);
          }
          ++counter;
 
          file << std::endl;
 
          // Write boundaries
          if (!physicalBoundaries.empty()) {
            auto refElement = referenceElement<typename GridView::ctype,dim>(entity.type());
            for(const auto& intersection : intersections(gv, entity)) {
              if(intersection.boundary()) {
                const auto faceLocalIndex(intersection.indexInInside());
                file << counter << " " << translateDuneToGmshType(intersection.type())
                  << " " << 1 << " " << physicalBoundaries[intersection.boundarySegmentIndex()];
                for (int k = 0; k < intersection.geometry().corners(); ++k)
                {
                  const auto vtxLocalIndex(refElement.subEntity(faceLocalIndex, 1, k, dim));
                  file << " " << nodeIndexFromEntity(entity, vtxLocalIndex);
                }
                ++counter;
                file << std::endl;
              }
            }
          }
 
        } catch(Exception& e) {
          file.close();
          throw;
        }
      }
    }
 
 
    void outputNodes(std::ofstream& file) const {
      for (const auto& vertex : vertices(gv)) {
        const auto globalCoord = vertex.geometry().center();
        const auto nodeIndex = gv.indexSet().index(vertex)+1; // Start counting indices by "1".
 
        if (1 == dimWorld)
          file << nodeIndex << " " << globalCoord[0] << " " << 0 << " " << 0 << std::endl;
        else if (2 == dimWorld)
          file << nodeIndex << " " << globalCoord[0] << " " << globalCoord[1] << " " << 0 << std::endl;
        else // (3 == dimWorld)
          file << nodeIndex << " " << globalCoord[0] << " " << globalCoord[1] << " " << globalCoord[2] << std::endl;
      }
    }
 
  public:
    GmshWriter(const GridView& gridView, int numDigits=6) : gv(gridView), precision(numDigits) {}
 
    void setPrecision(int numDigits) {
      precision = numDigits;
    }
 
    void write(const std::string& fileName,
               const std::vector<int>& physicalEntities=std::vector<int>(),
               const std::vector<int>& physicalBoundaries=std::vector<int>()) const {
      // Open file
      std::ofstream file(fileName.c_str());
      if (!file.is_open())
        DUNE_THROW(Dune::IOError, "Could not open " << fileName << " with write access.");
 
      // Set precision
      file << std::setprecision( precision );
 
      // Output Header
      file << "$MeshFormat" << std::endl
           << "2.0 0 " << sizeof(double) << std::endl // "2.0" for "version 2.0", "0" for ASCII
           << "$EndMeshFormat" << std::endl;
 
      // Output Nodes
      file << "$Nodes" << std::endl
           << gv.size(dim) << std::endl;
 
      outputNodes(file);
 
      file << "$EndNodes" << std::endl;
 
      // Output Elements;
      int boundariesSize(0);
      if(!physicalBoundaries.empty())
        for(const auto& entity : elements(gv))
          for(const auto& intersection : intersections(gv, entity))
            if(intersection.boundary())
              ++boundariesSize;
 
      file << "$Elements" << std::endl
           << gv.size(0) + boundariesSize<< std::endl;
 
      outputElements(file, physicalEntities, physicalBoundaries);
 
      file << "$EndElements" << std::endl;
    }
 
  };
 
} // namespace Dune
 
#endif // DUNE_GRID_IO_FILE_GMSHWRITER_HH