cell_hex.h

// The libMesh Finite Element Library.
// Copyright (C) 2002-2022 Benjamin S. Kirk, John W. Peterson, Roy H. Stogner

// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.

// This library 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.

// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA



#ifndef LIBMESH_CELL_HEX_H
#define LIBMESH_CELL_HEX_H

// Local includes
#include "libmesh/cell.h"

namespace libMesh
{

/**
 * The \p Hex is an element in 3D with 6 sides.
 *
 * \author Benjamin S. Kirk
 * \date 2002
 * \brief The base class for all hexahedral element types.
 */
class Hex : public Cell
{
public:

  /**
   * Default brick element, takes number of nodes and
   * parent. Derived classes implement 'true' elements.
   */
  Hex(const unsigned int nn, Elem * p, Node ** nodelinkdata) :
    Cell(nn, Hex::n_sides(), p, _elemlinks_data, nodelinkdata)
  {
    // Make sure the interior parent isn't undefined
    if (LIBMESH_DIM > 3)
      this->set_interior_parent(nullptr);
  }

  Hex (Hex &&) = delete;
  Hex (const Hex &) = delete;
  Hex & operator= (const Hex &) = delete;
  Hex & operator= (Hex &&) = delete;
  virtual ~Hex() = default;

  /**
   * \returns The \p Point associated with local \p Node \p i,
   * in master element rather than physical coordinates.
   */
  virtual Point master_point (const unsigned int i) const override final
  {
    libmesh_assert_less(i, this->n_nodes());
    return Point(_master_points[i][0],
                 _master_points[i][1],
                 _master_points[i][2]);
  }

  /**
   * \returns 6.
   */
  virtual unsigned int n_sides() const override final { return 6; }

  /**
   * \returns 8.  All hexahedra have 8 vertices.
   */
  virtual unsigned int n_vertices() const override final { return 8; }

  /**
   * \returns 4. Every side has four vertices.
   */
  virtual unsigned int n_vertices_on_side(const unsigned short libmesh_dbg_var(s)) const override final
  { libmesh_assert_less(s, this->n_sides()); return 4; }

  /**
   * \returns 12.  All hexahedra have 12 edges.
   */
  virtual unsigned int n_edges() const override final { return 12; }

  /**
   * \returns 6.  All hexahedra have 6 faces.
   */
  virtual unsigned int n_faces() const override final { return 6; }

  /**
   * \returns 8.
   */
  virtual unsigned int n_children() const override final { return 8; }

  /**
   * \returns \p true if the specified child is on the specified side.
   */
  virtual bool is_child_on_side(const unsigned int c,
                                const unsigned int s) const override final;

  /**
   * \returns \p true if the specified edge is on the specified side.
   */
  virtual bool is_edge_on_side(const unsigned int e,
                               const unsigned int s) const override final;

  /**
   * \returns The side number opposite to \p s (for a tensor product
   * element), or throws an error otherwise.
   */
  virtual unsigned int opposite_side(const unsigned int s) const override final;

  /**
   * \returns The local node number for the node opposite to node n
   * on side \p opposite_side(s) (for a tensor product element), or
   * throws an error otherwise.
   */
  virtual unsigned int opposite_node(const unsigned int n,
                                     const unsigned int s) const override final;

  /**
   * Don't hide Elem::key() defined in the base class.
   */
  using Elem::key;

  /**
   * \returns An id associated with the \p s side of this element.
   * The id is not necessarily unique, but should be close.  This is
   * particularly useful in the \p MeshBase::find_neighbors() routine.
   */
  virtual dof_id_type key (const unsigned int s) const override;

  /**
   * \returns \p Hex8::side_nodes_map[side][side_node] after doing some range checking.
   */
  virtual unsigned int local_side_node(unsigned int side,
                                       unsigned int side_node) const override;

  /**
   * \returns \p Hex8::edge_nodes_map[edge][edge_node] after doing some range checking.
   */
  virtual unsigned int local_edge_node(unsigned int edge,
                                       unsigned int edge_node) const override;

  /**
   * \returns A primitive (4-noded) quad for face i.
   */
  virtual std::unique_ptr<Elem> side_ptr (const unsigned int i) override final;

  /**
   * Rebuilds a primitive (4-noded) quad for face i.
   */
  virtual void side_ptr (std::unique_ptr<Elem> & side, const unsigned int i) override final;

  /**
   * \returns A quantitative assessment of element quality based on
   * the quality metric \p q specified by the user.
   */
  virtual Real quality (const ElemQuality q) const override;

  /**
   * \returns The suggested quality bounds for the hex based on
   * quality measure \p q.  These are the values suggested by the
   * CUBIT User's Manual.
   */
  virtual std::pair<Real, Real> qual_bounds (const ElemQuality q) const override;

  virtual std::vector<unsigned int> sides_on_edge(const unsigned int e) const override final;

  /**
   * Six sides, four orientations per side.
   */
  virtual unsigned int n_permutations() const override final { return 24; }

  virtual void orient(BoundaryInfo *) override final;

  /**
   * This maps each edge to the sides that contain said edge.
   */
  static const unsigned int edge_sides_map[12][2];

protected:

  /**
   * Data for links to parent/neighbor/interior_parent elements.
   */
  Elem * _elemlinks_data[7+(LIBMESH_DIM>3)];

  /**
   * Matrix that tells which vertices define the location
   * of mid-side (or second-order) nodes.  This matrix
   * is kept here, since the matrix (for the first 12
   * higher-order nodes) is identical for \p Hex20 and
   * \p Hex27.
   */
  static const unsigned short int _second_order_adjacent_vertices[12][2];

  /**
   * Vector that names a child sharing each second order node.
   */
  static const unsigned short int _second_order_vertex_child_number[27];

  /**
   * Vector that names the child vertex index for each second order node.
   */
  static const unsigned short int _second_order_vertex_child_index[27];

  /**
   * Master element node locations
   */
  static const Real _master_points[27][3];

  /**
   * Lookup table from child id, child node id to "possible node
   * location" (a simple dictionary-index in a 5x5x5 grid)
   */
  static const int _child_node_lookup[8][27];
};

} // namespace libMesh

#endif // LIBMESH_CELL_HEX_H