tetrahedron.hpp

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// Copyright (c) 2010-2025, 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.
 
#ifndef MFEM_TETRAHEDRON
#define MFEM_TETRAHEDRON
 
#include "../config/config.hpp"
#include "element.hpp"
 
namespace mfem
{
 
/// Data type tetrahedron element
class Tetrahedron : public Element
{
protected:
   int indices[4];
 
   /** The refinement flag keeps (in order) :
       1. Two marked edges given with local index (0..5) for the two faces
       that don't have the refinement edge as edge. The refinement edge
       is determined by the first two nodes of the tetrahedron. Each
       marked edge is stored in 3 bits (or as implemented in the functions
       CreateRefinementFlag and ParseRefinementFlag.
       2. Type of the element, stored in the next 3 bits.
       3. The rest is free for now. **/
   int refinement_flag;
 
   unsigned transform;
 
public:
   typedef Geometry::Constants<Geometry::TETRAHEDRON> geom_t;
 
   /// Constants for different types of tetrahedrons.
   enum { TYPE_PU=0, TYPE_A=1, TYPE_PF=2, TYPE_O=3, TYPE_M=4 };
 
   Tetrahedron() : Element(Geometry::TETRAHEDRON)
   { refinement_flag = 0; transform = 0; }
 
   /// Constructs tetrahedron by specifying the indices and the attribute.
   Tetrahedron(const int *ind, int attr = 1);
 
   /// Constructs tetrahedron by specifying the indices and the attribute.
   Tetrahedron(int ind1, int ind2, int ind3, int ind4, int attr = 1);
 
   /// Initialize the vertex indices and the attribute of a Tetrahedron.
   void Init(int ind1, int ind2, int ind3, int ind4, int attr = 1,
             int ref_flag = 0);
 
   /// Return element's type.
   Type GetType() const override { return Element::TETRAHEDRON; }
 
   void  ParseRefinementFlag(int refinement_edges[2], int &type,
                             int &flag) const;
   void CreateRefinementFlag(int refinement_edges[2], int  type, int  flag = 0);
 
   void GetMarkedFace(const int face, int *fv) const;
 
   int GetRefinementFlag() const { return refinement_flag; }
 
   void SetRefinementFlag(int rf) { refinement_flag = rf; }
 
   /// Return 1 if the element needs refinement in order to get conforming mesh.
   int NeedRefinement(HashTable<Hashed2> &v_to_v) const override;
 
   /** Reorder the vertices so that the longest edge is from vertex 0
       to vertex 1. If called it should be once from the mesh constructor,
       because the order may be used later for setting the edges. **/
   void MarkEdge(const DSTable &v_to_v, const int *length) override;
 
   void ResetTransform(int tr) override { transform = tr; }
   unsigned GetTransform() const override { return transform; }
 
   /// Add 'tr' to the current chain of coarse-fine transformations.
   void PushTransform(int tr) override
   { transform = (transform << 3) | (tr + 1); }
 
   /// Calculate point matrix corresponding to a chain of transformations.
   static void GetPointMatrix(unsigned transform, DenseMatrix &pm);
 
   /// Get the indices defining the vertices.
   void GetVertices(Array<int> &v) const override;
 
   /// Set the indices defining the vertices.
   void SetVertices(const Array<int> &v) override;
 
   /// @note The returned array should NOT be deleted by the caller.
   int * GetVertices () override { return indices; }
 
   /// Set the indices defining the vertices.
   void SetVertices(const int *ind) override;
 
   int GetNVertices() const override { return 4; }
 
   int GetNEdges() const override { return (6); }
 
   const int *GetEdgeVertices(int ei) const override
   { return geom_t::Edges[ei]; }
 
   /// @deprecated Use GetNFaces(void) and GetNFaceVertices(int) instead.
   MFEM_DEPRECATED int GetNFaces(int &nFaceVertices) const override
   { nFaceVertices = 3; return 4; }
 
   int GetNFaces() const override { return 4; }
 
   int GetNFaceVertices(int) const override { return 3; }
 
   const int *GetFaceVertices(int fi) const override
   { return geom_t::FaceVert[fi]; }
 
   Element *Duplicate(Mesh *m) const override;
 
   virtual ~Tetrahedron() = default;
};
 
// Defined in fe.cpp to ensure construction before 'mfem::Geometries'.
extern MFEM_EXPORT class Linear3DFiniteElement TetrahedronFE;
 
}
 
#endif