mesh_extras.cpp

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// Copyright (c) 2010-2020, Lawrence Livermore National Security, LLC. Produced
// at the Lawrence Livermore National Laboratory. All Rights reserved. See files
// LICENSE and NOTICE for details. LLNL-CODE-806117.
//
// This file is part of the MFEM library. For more information and source code
// availability visit https://mfem.org.
//
// MFEM is free software; you can redistribute it and/or modify it under the
// terms of the BSD-3 license. We welcome feedback and contributions, see file
// CONTRIBUTING.md for details.

#include "mesh_extras.hpp"

using namespace std;

namespace mfem
{

namespace common
{

ElementMeshStream::ElementMeshStream(Element::Type e)
{
   *this << "MFEM mesh v1.0" << endl;
   switch (e)
   {
      case Element::SEGMENT:
         *this << "dimension" << endl << 1 << endl
               << "elements" << endl << 1 << endl
               << "1 1 0 1" << endl
               << "boundary" << endl << 2 << endl
               << "1 0 0" << endl
               << "1 0 1" << endl
               << "vertices" << endl
               << 2 << endl
               << 1 << endl
               << 0 << endl
               << 1 << endl;
         break;
      case Element::TRIANGLE:
         *this << "dimension" << endl << 2 << endl
               << "elements" << endl << 1 << endl
               << "1 2 0 1 2" << endl
               << "boundary" << endl << 3 << endl
               << "1 1 0 1" << endl
               << "1 1 1 2" << endl
               << "1 1 2 0" << endl
               << "vertices" << endl
               << "3" << endl
               << "2" << endl
               << "0 0" << endl
               << "1 0" << endl
               << "0 1" << endl;
         break;
      case Element::QUADRILATERAL:
         *this << "dimension" << endl << 2 << endl
               << "elements" << endl << 1 << endl
               << "1 3 0 1 2 3" << endl
               << "boundary" << endl << 4 << endl
               << "1 1 0 1" << endl
               << "1 1 1 2" << endl
               << "1 1 2 3" << endl
               << "1 1 3 0" << endl
               << "vertices" << endl
               << "4" << endl
               << "2" << endl
               << "0 0" << endl
               << "1 0" << endl
               << "1 1" << endl
               << "0 1" << endl;
         break;
      case Element::TETRAHEDRON:
         *this << "dimension" << endl << 3 << endl
               << "elements" << endl << 1 << endl
               << "1 4 0 1 2 3" << endl
               << "boundary" << endl << 4 << endl
               << "1 2 0 2 1" << endl
               << "1 2 1 2 3" << endl
               << "1 2 2 0 3" << endl
               << "1 2 0 1 3" << endl
               << "vertices" << endl
               << "4" << endl
               << "3" << endl
               << "0 0 0" << endl
               << "1 0 0" << endl
               << "0 1 0" << endl
               << "0 0 1" << endl;
         break;
      case Element::HEXAHEDRON:
         *this << "dimension" << endl << 3 << endl
               << "elements" << endl << 1 << endl
               << "1 5 0 1 2 3 4 5 6 7" << endl
               << "boundary" << endl << 6 << endl
               << "1 3 0 3 2 1" << endl
               << "1 3 4 5 6 7" << endl
               << "1 3 0 1 5 4" << endl
               << "1 3 1 2 6 5" << endl
               << "1 3 2 3 7 6" << endl
               << "1 3 3 0 4 7" << endl
               << "vertices" << endl
               << "8" << endl
               << "3" << endl
               << "0 0 0" << endl
               << "1 0 0" << endl
               << "1 1 0" << endl
               << "0 1 0" << endl
               << "0 0 1" << endl
               << "1 0 1" << endl
               << "1 1 1" << endl
               << "0 1 1" << endl;
         break;
      default:
         mfem_error("Invalid element type!");
         break;
   }

}

void
MergeMeshNodes(Mesh * mesh, int logging)
{
   int dim  = mesh->Dimension();
   int sdim = mesh->SpaceDimension();

   double h_min, h_max, k_min, k_max;
   mesh->GetCharacteristics(h_min, h_max, k_min, k_max);

   // Set tolerance for merging vertices
   double tol = 1.0e-8 * h_min;

   if ( logging > 0 )
      cout << "Euler Number of Initial Mesh:  "
           << ((dim==3)?mesh->EulerNumber() :
               ((dim==2)?mesh->EulerNumber2D() :
                mesh->GetNV() - mesh->GetNE())) << endl;

   vector<int> v2v(mesh->GetNV());

   Vector vd(sdim);

   for (int i = 0; i < mesh->GetNV(); i++)
   {
      Vector vi(mesh->GetVertex(i), sdim);

      v2v[i] = -1;

      for (int j = 0; j < i; j++)
      {
         Vector vj(mesh->GetVertex(j), sdim);
         add(vi, -1.0, vj, vd);

         if ( vd.Norml2() < tol )
         {
            v2v[i] = j;
            break;
         }
      }
      if ( v2v[i] < 0 ) { v2v[i] = i; }
   }

   // renumber elements
   for (int i = 0; i < mesh->GetNE(); i++)
   {
      Element *el = mesh->GetElement(i);
      int *v = el->GetVertices();
      int nv = el->GetNVertices();
      for (int j = 0; j < nv; j++)
      {
         v[j] = v2v[v[j]];
      }
   }
   // renumber boundary elements
   for (int i = 0; i < mesh->GetNBE(); i++)
   {
      Element *el = mesh->GetBdrElement(i);
      int *v = el->GetVertices();
      int nv = el->GetNVertices();
      for (int j = 0; j < nv; j++)
      {
         v[j] = v2v[v[j]];
      }
   }

   mesh->RemoveUnusedVertices();

   if ( logging > 0 )
   {
      cout << "Euler Number of Final Mesh:    "
           << ((dim==3) ? mesh->EulerNumber() :
               ((dim==2) ? mesh->EulerNumber2D() :
                mesh->GetNV() - mesh->GetNE()))
           << endl;
   }
}

} // namespace common

} // namespace mfem