text: /**
   * \file
   * \copyright
   * Copyright (c) 2012-2020, OpenGeoSys Community (http://www.opengeosys.org)
   *            Distributed under a Modified BSD License.
   *              See accompanying file LICENSE.txt or
   *              http://www.opengeosys.org/project/license
   *
   */
  
  #pragma once
  
  #include "MeshLib/MeshEnums.h"
  #include "Element.h"
  #include "EdgeReturn.h"
  #include "CellRule.h"
  
  namespace MeshLib
  {
  
  /**
   * This class represents a 3d tetrahedron element. The following sketch shows the node and edge numbering.
   * @anchor Tetrahedron4NodeAndEdgeNumbering
   * @code
   *          3
   *         /|\
   *        / | \
   *      3/  |  \5
   *      /   |4  \
   *     /    |    \
   *    0.....|.....2
   *     \    |  2 /
   *      \   |   /
   *      0\  |  /1
   *        \ | /
   *         \|/
   *          1
   *
   * @endcode
   */
  class TetRule4 : public CellRule
  {
  public:
      /// Constant: The number of base nodes for this element
      static const unsigned n_base_nodes = 4u;
  
      /// Constant: The number of all nodes for this element
      static const unsigned n_all_nodes = 4u;
  
      /// Constant: The geometric type of the element
      static const MeshElemType mesh_elem_type = MeshElemType::TETRAHEDRON;
  
      /// Constant: The FEM type of the element
      static const CellType cell_type = CellType::TET4;
  
      /// Constant: The number of faces
      static const unsigned n_faces = 4;
  
      /// Constant: The number of edges
      static const unsigned n_edges = 6;
  
      /// Constant: The number of neighbors
      static const unsigned n_neighbors = 4;
  
      /// Constant: Local node index table for faces
      static const unsigned face_nodes[4][3];
  
      /// Constant: Local node index table for edge
      static const unsigned edge_nodes[6][2];
  
      /// Returns the i-th edge of the element.
      using EdgeReturn = MeshLib::LinearEdgeReturn;
  
      /// Returns the i-th face of the element.
      static const Element* getFace(const Element* e, unsigned i);
  
      /**
       * \copydoc MeshLib::Element::isPntInElement()
       * @param nodes the nodes of the element.
       */
      static bool isPntInElement(Node const* const* nodes,
                                 MathLib::Point3d const& pnt, double eps);
  
      /**
       * Tests if the element is geometrically valid.
       */
      static ElementErrorCode validate(const Element* e);
  
      /// Returns the ID of a face given an array of nodes.
      static unsigned identifyFace(Node const* const* /*_nodes*/, Node* nodes[3]);
  
      /// Calculates the volume of the element
      static double computeVolume(Node const* const* _nodes);
  
  }; /* class */
  
  }  // namespace MeshLib
  