prism_rules_impl.h

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/*
 * Copyright (c) 2015:  G-CSC, Goethe University Frankfurt
 * Author: Sebastian Reiter
 * 
 * This file is part of UG4.
 * 
 * UG4 is free software: you can redistribute it and/or modify it under the
 * terms of the GNU Lesser General Public License version 3 (as published by the
 * Free Software Foundation) with the following additional attribution
 * requirements (according to LGPL/GPL v3 §7):
 * 
 * (1) The following notice must be displayed in the Appropriate Legal Notices
 * of covered and combined works: "Based on UG4 (www.ug4.org/license)".
 * 
 * (2) The following notice must be displayed at a prominent place in the
 * terminal output of covered works: "Based on UG4 (www.ug4.org/license)".
 * 
 * (3) The following bibliography is recommended for citation and must be
 * preserved in all covered files:
 * "Reiter, S., Vogel, A., Heppner, I., Rupp, M., and Wittum, G. A massively
 *   parallel geometric multigrid solver on hierarchically distributed grids.
 *   Computing and visualization in science 16, 4 (2013), 151-164"
 * "Vogel, A., Reiter, S., Rupp, M., Nägel, A., and Wittum, G. UG4 -- a novel
 *   flexible software system for simulating pde based models on high performance
 *   computers. Computing and visualization in science 16, 4 (2013), 165-179"
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Lesser General Public License for more details.
 */
 
#ifndef __H__UG_prism_rules_impl
#define __H__UG_prism_rules_impl
 
#include "prism_rules.h"
#include "grid_object_ids.h"
 
namespace ug{
namespace prism_rules{
 
template <class TCmp>
int ConvertToTetrahedra(int* newIndsOut, TCmp cmp)
{
//  The idea and implementation follows:
//  Dompierre et al., "How to Subdivide Pyramids, Prisms and Hexahedra into Tetrahedra"
 
//  find the smallest index
  int smallest = 0;
  for(int i = 1; i < 6; ++i){
    if(cmp(i, smallest))
      smallest = i;
  }
 
//  create a local ordering
  static const int permutations [6][6] = {{0, 1, 2, 3, 4, 5},
                      {1, 2, 0, 4, 5, 3},
                      {2, 0, 1, 5, 3, 4},
                      {3, 5, 4, 0, 2, 1},
                      {4, 3, 5, 1, 0, 2},
                      {5, 4, 3, 2, 1, 0}};
 
  const int* I = permutations[smallest];
 
  int t0 = cmp(I[1], I[5])  ? I[1] : I[5];
  int t1 = cmp(I[2], I[4])  ? I[2] : I[4];
 
  if(cmp(t0, t1)){
    int i = 0;
    newIndsOut[i++] = GOID_TETRAHEDRON;
    newIndsOut[i++] = I[0]; newIndsOut[i++] = I[1];
    newIndsOut[i++] = I[2]; newIndsOut[i++] = I[5];
 
    newIndsOut[i++] = GOID_TETRAHEDRON;
    newIndsOut[i++] = I[0]; newIndsOut[i++] = I[1];
    newIndsOut[i++] = I[5]; newIndsOut[i++] = I[4];
 
    newIndsOut[i++] = GOID_TETRAHEDRON;
    newIndsOut[i++] = I[0]; newIndsOut[i++] = I[4];
    newIndsOut[i++] = I[5]; newIndsOut[i++] = I[3];
    return i;
  }
  else{
    int i = 0;
    newIndsOut[i++] = GOID_TETRAHEDRON;
    newIndsOut[i++] = I[0]; newIndsOut[i++] = I[1];
    newIndsOut[i++] = I[2]; newIndsOut[i++] = I[4];
 
    newIndsOut[i++] = GOID_TETRAHEDRON;
    newIndsOut[i++] = I[0]; newIndsOut[i++] = I[4];
    newIndsOut[i++] = I[2]; newIndsOut[i++] = I[5];
 
    newIndsOut[i++] = GOID_TETRAHEDRON;
    newIndsOut[i++] = I[0]; newIndsOut[i++] = I[4];
    newIndsOut[i++] = I[5]; newIndsOut[i++] = I[3];
    return i;
  }
}
 
}// end of namespace  
}// end of namespace
 
#endif  //__H__UG_prism_rules_impl