/home/hauberg/Dokumenter/Capture/humim-tracker-0.1/src/OpenTissue/OpenTissue/dynamics/fem/fem_stiffness_assembly.h

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#ifndef OPENTISSUE_DYNAMICS_FEM_FEM_STIFFNESS_ASSEMBLY_H
#define OPENTISSUE_DYNAMICS_FEM_FEM_STIFFNESS_ASSEMBLY_H
//
// OpenTissue Template Library
// - A generic toolbox for physics-based modeling and simulation.
// Copyright (C) 2008 Department of Computer Science, University of Copenhagen.
//
// OTTL is licensed under zlib: http://opensource.org/licenses/zlib-license.php
//
#include <OpenTissue/configuration.h>

namespace OpenTissue
{
  namespace fem
  {
    namespace detail
    {
      template<typename tetrahedron_iterator>
      inline void stiffness_assembly(tetrahedron_iterator const & begin, tetrahedron_iterator const & end)
      {
        typedef typename tetrahedron_iterator::value_type::real_type        real_type;
        typedef typename tetrahedron_iterator::value_type::vector3_type     vector3_type;
        typedef typename tetrahedron_iterator::value_type::matrix3x3_type   matrix3x3_type;
        typedef typename tetrahedron_iterator::value_type::node_iterator    node_iterator;

        for(tetrahedron_iterator T = begin;T!=end;++T)
        {
          matrix3x3_type & Re = T->m_Re;
          for (int i = 0; i < 4; ++i)
          {
            node_iterator p_i = T->node(i);
            vector3_type f;
            f.clear();
            for (int j = 0; j < 4; ++j)
            {
              node_iterator    p_j   = T->node(j);
              matrix3x3_type & Ke_ij = T->m_Ke[i][j];
              vector3_type   & x0_j  = p_j->m_model_coord;

              f += Ke_ij * x0_j;
              if (j >= i)
              {

                matrix3x3_type tmp = Re * Ke_ij * trans(Re);

                p_i->K(p_j->idx()) += tmp;
                if (j > i)
                  p_j->K(p_i->idx()) += trans(tmp);
              }
            }

            p_i->m_f0 -= Re*f;

          }
        }
      }

    } // namespace detail
  } // namespace fem
} // namespace OpenTissue

//OPENTISSUE_DYNAMICS_FEM_FEM_STIFFNESS_ASSEMBLY_H
#endif