text: // This file is part of libigl, a simple c++ geometry processing library.
  // 
  // Copyright (C) 2013 Alec Jacobson <alecjacobson@gmail.com>
  // 
  // This Source Code Form is subject to the terms of the Mozilla Public License 
  // v. 2.0. If a copy of the MPL was not distributed with this file, You can 
  // obtain one at http://mozilla.org/MPL/2.0/.
  #include "writeMESH.h"
  
  #include "verbose.h"
  #include "list_to_matrix.h"
  #include <Eigen/Core>
  
  #include <iostream>
  #include <fstream>
  #include <cstdio>
  
  template <typename Scalar, typename Index>
  IGL_INLINE bool igl::writeMESH(
    const std::string mesh_file_name,
    const std::vector<std::vector<Scalar > > & V,
    const std::vector<std::vector<Index > > & T,
    const std::vector<std::vector<Index > > & F)
  {
    Eigen::MatrixXd mV;
    Eigen::MatrixXi mT,mF;
    bool is_rect;
    is_rect = list_to_matrix(V,mV);
    if(!is_rect)
    {
      return false;
    }
    is_rect = list_to_matrix(T,mT);
    if(!is_rect)
    {
      return false;
    }
    is_rect = list_to_matrix(F,mF);
    if(!is_rect)
    {
      return false;
    }
    return igl::writeMESH(mesh_file_name,mV,mT,mF);
  }
  
  
  template <typename DerivedV, typename DerivedT, typename DerivedF>
  IGL_INLINE bool igl::writeMESH(
    const std::string str,
    const Eigen::PlainObjectBase<DerivedV> & V, 
    const Eigen::PlainObjectBase<DerivedT> & T,
    const Eigen::PlainObjectBase<DerivedF> & F)
  {
    using namespace std;
    using namespace Eigen;
  
    //// This is (surprisingly) slower than the C-ish code below
    //ofstream mesh_file;
    //mesh_file.open(str.c_str());
    //if(!mesh_file.is_open())
    //{
    //  cerr<<"IOError: "<<str<<" could not be opened..."<<endl;
    //  return false;
    //}
    //IOFormat format(FullPrecision,DontAlignCols," ","\n",""," 1","","");
    //mesh_file<<"MeshVersionFormatted 1\n";
    //mesh_file<<"Dimension 3\n";
    //mesh_file<<"Vertices\n";
    //mesh_file<<V.rows()<<"\n";
    //mesh_file<<V.format(format)<<"\n";
    //mesh_file<<"Triangles\n";
    //mesh_file<<F.rows()<<"\n";
    //mesh_file<<(F.array()+1).eval().format(format)<<"\n";
    //mesh_file<<"Tetrahedra\n";
    //mesh_file<<T.rows()<<"\n";
    //mesh_file<<(T.array()+1).eval().format(format)<<"\n";
    //mesh_file.close();
  
    FILE * mesh_file = fopen(str.c_str(),"w");
    if(NULL==mesh_file)
    {
      fprintf(stderr,"IOError: %s could not be opened...",str.c_str());
      return false;
    }
    // print header
    fprintf(mesh_file,"MeshVersionFormatted 1\n");
    fprintf(mesh_file,"Dimension 3\n");
    // print tet vertices
    fprintf(mesh_file,"Vertices\n");
    // print number of tet vertices
    int number_of_tet_vertices = V.rows();
    fprintf(mesh_file,"%d\n",number_of_tet_vertices);
    // loop over tet vertices
    for(int i = 0;i<number_of_tet_vertices;i++)
    {
      // print position of ith tet vertex
      fprintf(mesh_file,"%.17lg %.17lg %.17lg 1\n",
        (double)V(i,0),
        (double)V(i,1),
        (double)V(i,2));
    }
    verbose("WARNING: save_mesh() assumes that vertices have"
        " same indices in surface as volume...\n");
    // print faces
    fprintf(mesh_file,"Triangles\n");
    // print number of triangles
    int number_of_triangles = F.rows();
    fprintf(mesh_file,"%d\n",number_of_triangles);
    // loop over faces
    for(int i = 0;i<number_of_triangles;i++)
    {
      // loop over vertices in face
      fprintf(mesh_file,"%d %d %d 1\n", 
        (int)F(i,0)+1, 
        (int)F(i,1)+1, 
        (int)F(i,2)+1);
    }
    // print tetrahedra
    fprintf(mesh_file,"Tetrahedra\n");
    int number_of_tetrahedra = T.rows();
    // print number of tetrahedra
    fprintf(mesh_file,"%d\n",number_of_tetrahedra);
    // loop over tetrahedra
    for(int i = 0; i < number_of_tetrahedra;i++)
    {
      // mesh standard uses 1-based indexing
      fprintf(mesh_file, "%d %d %d %d 1\n",
        (int)T(i,0)+1,
        (int)T(i,1)+1,
        (int)T(i,2)+1,
        (int)T(i,3)+1);
    }
    fclose(mesh_file);
    return true;
  }
  
  #ifdef IGL_STATIC_LIBRARY
  // Explicit template specialization
  // generated by autoexplicit.sh
  template bool igl::writeMESH<Eigen::Matrix<double, -1, 3, 0, -1, 3>, Eigen::Matrix<int, -1, -1, 0, -1, -1>, Eigen::Matrix<int, -1, 3, 0, -1, 3> >(std::basic_string<char, std::char_traits<char>, std::allocator<char> >, Eigen::PlainObjectBase<Eigen::Matrix<double, -1, 3, 0, -1, 3> > const&, Eigen::PlainObjectBase<Eigen::Matrix<int, -1, -1, 0, -1, -1> > const&, Eigen::PlainObjectBase<Eigen::Matrix<int, -1, 3, 0, -1, 3> > const&);
  // generated by autoexplicit.sh
  template bool igl::writeMESH<Eigen::Matrix<double, 8, 3, 0, 8, 3>, Eigen::Matrix<int, -1, -1, 0, -1, -1>, Eigen::Matrix<int, 12, 3, 0, 12, 3> >(std::basic_string<char, std::char_traits<char>, std::allocator<char> >, Eigen::PlainObjectBase<Eigen::Matrix<double, 8, 3, 0, 8, 3> > const&, Eigen::PlainObjectBase<Eigen::Matrix<int, -1, -1, 0, -1, -1> > const&, Eigen::PlainObjectBase<Eigen::Matrix<int, 12, 3, 0, 12, 3> > const&);
  //template bool igl::writeMESH<Eigen::Matrix<double, -1, -1, 0, -1, -1>, Eigen::Matrix<int, -1, -1, 0, -1, -1>, Eigen::Matrix<int, -1, -1, 0, -1, -1> >(std::basic_string<char, std::char_traits<char>, std::allocator<char> >, Eigen::MatrixBase<Eigen::Matrix<double, -1, -1, 0, -1, -1> > const&, Eigen::MatrixBase<Eigen::Matrix<int, -1, -1, 0, -1, -1> > const&, Eigen::MatrixBase<Eigen::Matrix<int, -1, -1, 0, -1, -1> > const&);
  template bool igl::writeMESH<Eigen::Matrix<double, -1, -1, 0, -1, -1>, Eigen::Matrix<int, -1, -1, 0, -1, -1>, Eigen::Matrix<int, -1, -1, 0, -1, -1> >(std::basic_string<char, std::char_traits<char>, std::allocator<char> >, Eigen::PlainObjectBase<Eigen::Matrix<double, -1, -1, 0, -1, -1> > const&, Eigen::PlainObjectBase<Eigen::Matrix<int, -1, -1, 0, -1, -1> > const&, Eigen::PlainObjectBase<Eigen::Matrix<int, -1, -1, 0, -1, -1> > const&);
  
  template bool igl::writeMESH<Eigen::Matrix<double, -1, -1, 0, -1, -1>, Eigen::Matrix<double, -1, -1, 0, -1, -1>, Eigen::Matrix<int, -1, -1, 0, -1, -1> >(std::basic_string<char, std::char_traits<char>, std::allocator<char> >, Eigen::PlainObjectBase<Eigen::Matrix<double, -1, -1, 0, -1, -1> > const&, Eigen::PlainObjectBase<Eigen::Matrix<double, -1, -1, 0, -1, -1> > const&, Eigen::PlainObjectBase<Eigen::Matrix<int, -1, -1, 0, -1, -1> > const&);
  template bool igl::writeMESH<double, int>(std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::vector<std::vector<double, std::allocator<double> >, std::allocator<std::vector<double, std::allocator<double> > > > const&, std::vector<std::vector<int, std::allocator<int> >, std::allocator<std::vector<int, std::allocator<int> > > > const&, std::vector<std::vector<int, std::allocator<int> >, std::allocator<std::vector<int, std::allocator<int> > > > const&);
  #endif
  