Line data    Source code

       1             : // The libMesh Finite Element Library.
       2             : // Copyright (C) 2002-2026 Benjamin S. Kirk, John W. Peterson, Roy H. Stogner
       3             : 
       4             : // This library is free software; you can redistribute it and/or
       5             : // modify it under the terms of the GNU Lesser General Public
       6             : // License as published by the Free Software Foundation; either
       7             : // version 2.1 of the License, or (at your option) any later version.
       8             : 
       9             : // This library is distributed in the hope that it will be useful,
      10             : // but WITHOUT ANY WARRANTY; without even the implied warranty of
      11             : // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      12             : // Lesser General Public License for more details.
      13             : 
      14             : // You should have received a copy of the GNU Lesser General Public
      15             : // License along with this library; if not, write to the Free Software
      16             : // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
      17             : 
      18             : 
      19             : #ifndef LIBMESH_MESH_TET_INTERFACE_H
      20             : #define LIBMESH_MESH_TET_INTERFACE_H
      21             : 
      22             : #include "libmesh/libmesh_config.h"
      23             : 
      24             : // Local includes
      25             : #include "libmesh/bounding_box.h"
      26             : #include "libmesh/enum_elem_type.h"
      27             : #include "libmesh/point.h" // used for specifying holes
      28             : 
      29             : // C++ includes
      30             : #include <cstddef>
      31             : #include <map>
      32             : #include <memory>
      33             : #include <string>
      34             : #include <vector>
      35             : 
      36             : namespace libMesh
      37             : {
      38             : // Forward Declarations
      39             : class UnstructuredMesh;
      40             : class Elem;
      41             : 
      42             : /**
      43             :  * Class \p MeshTetInterface provides an abstract interface for
      44             :  * tetrahedralization of meshes by subclasses.
      45             :  *
      46             :  * \author Roy H. Stogner
      47             :  * \date 2024
      48             :  */
      49          56 : class MeshTetInterface
      50             : {
      51             : public:
      52             : 
      53             :   /**
      54             :    * Constructor. Takes a reference to the mesh.
      55             :    */
      56             :   explicit
      57             :   MeshTetInterface (UnstructuredMesh & mesh);
      58             : 
      59             :   /**
      60             :    * Default destructor in base class.
      61             :    */
      62             :   virtual ~MeshTetInterface();
      63             : 
      64             :   /**
      65             :    * Sets and/or gets the desired tetrahedron volume.  Set to zero to
      66             :    * disable volume constraint.
      67             :    */
      68           0 :   Real & desired_volume() {return _desired_volume;}
      69             : 
      70             :   /**
      71             :    * Sets/gets flag which tells whether to do two steps of Laplace
      72             :    * mesh smoothing after generating the grid.  False by default (for
      73             :    * compatibility with old TetGenMeshInterface behavior).
      74             :    */
      75             :   bool & smooth_after_generating() {return _smooth_after_generating;}
      76             : 
      77             :   /**
      78             :    * Sets and/or gets the desired element type.  This should be a Tet
      79             :    * type.
      80             :    */
      81             :   ElemType & elem_type() {return _elem_type;}
      82             : 
      83             :   /**
      84             :    * Attaches a vector of Mesh pointers defining holes which will be
      85             :    * meshed around.  We use unique_ptr here because we expect that we
      86             :    * may need to modify these meshes internally.
      87             :    */
      88             :   void attach_hole_list(std::unique_ptr<std::vector<std::unique_ptr<UnstructuredMesh>>> holes);
      89             : 
      90             :   /**
      91             :    * This is the main public interface for this function.
      92             :    */
      93             :   virtual void triangulate () = 0;
      94             : 
      95             :   /**
      96             :    * Sets a verbosity level, defaulting to 0 (print nothing), to be
      97             :    * set as high as 100 (print everything).
      98             :    *
      99             :    * For verbosity >= 50, print all detected surface mesh integrity
     100             :    * issues as they're found.  Subclasses may add other output at
     101             :    * other verbosity levels.
     102             :    */
     103             :   void set_verbosity(unsigned int v);
     104             : 
     105             : protected:
     106             : 
     107             :   /**
     108             :    * verbosity setting
     109             :    */
     110             :   unsigned int _verbosity;
     111             : 
     112             :   /**
     113             :    * Remove volume elements from the given mesh, after converting
     114             :    * their outer boundary faces to surface elements.
     115             :    *
     116             :    * Returns the bounding box of the mesh; this is useful for
     117             :    * detecting misplaced holes later.
     118             :    */
     119             :   static BoundingBox volume_to_surface_mesh (UnstructuredMesh & mesh);
     120             : 
     121             :   /**
     122             :    * Enumeration of possible surface mesh integrity issues.
     123             :    */
     124             :   enum SurfaceIntegrity {
     125             :     NON_TRI3 = 1,           // a non-TRI3 element is found
     126             :     MISSING_NEIGHBOR = 2,   // an element with a nullptr-neighbor is found
     127             :     EMPTY_MESH = 3,         // the mesh is empty
     128             :     MISSING_BACKLINK = 4,   // an element neighbor isn't linked back to it
     129             :     BAD_NEIGHBOR_NODES = 5, // an element neighbor isn't linked to expected nodes
     130             :     NON_ORIENTED = 6,       // an element neighbor has inconsistent orientation
     131             :     BAD_NEIGHBOR_LINKS = 7, // an element neighbor has other inconsistent links
     132             :     DEGENERATE_ELEMENT = 8, // an element has zero area
     133             :     DEGENERATE_MESH = 9     // the mesh clearly bounds zero volume
     134             :   };
     135             : 
     136             :   /**
     137             :    * This function checks the integrity of the current set of
     138             :    * elements in the Mesh to see if they comprise a topological
     139             :    * manifold that (if it's also geometrically valid) would define
     140             :    * valid boundary for a tetrahedralized volume.
     141             :    *
     142             :    * Named \p check_hull_integrity() for backward compatibility, but
     143             :    * now accepts non-convex manifolds.
     144             :    *
     145             :    * \returns a set of \p  enums describing problems
     146             :    * found, or an empty set if no problems are found.
     147             :    */
     148             :   [[nodiscard]] std::set<SurfaceIntegrity> check_hull_integrity() const;
     149             : 
     150             :   /**
     151             :    * This function checks the integrity of the current set of
     152             :    * elements in the Mesh, and corrects what it can.
     153             :    *
     154             :    * \returns A set of SurfaceIntegrity codes from \p
     155             :    * check_hull_integrity() if there are problems it can't fix, or an
     156             :    * empty set otherwise.
     157             :    */
     158             :   [[nodiscard]] std::set<SurfaceIntegrity> improve_hull_integrity();
     159             : 
     160             :   /**
     161             :    * This function prints an informative message and throws an
     162             :    * exception based on the output of the check_hull_integrity()
     163             :    * function.  It is a separate function so that you can check hull
     164             :    * integrity without exiting or catching an exception if desired.
     165             :    */
     166             :   void process_hull_integrity_result(const std::set<SurfaceIntegrity> & result) const;
     167             : 
     168             :   /**
     169             :    * Delete original convex hull elements from the Mesh
     170             :    * after performing a Delaunay tetrahedralization.
     171             :    */
     172             :   void delete_2D_hull_elements();
     173             : 
     174             :   /**
     175             :    * The desired volume for the elements in the resulting mesh.
     176             :    * Unlimited (indicated by 0) by default
     177             :    */
     178             :   Real _desired_volume;
     179             : 
     180             :   /**
     181             :    * Flag which tells whether we should smooth the mesh after
     182             :    * it is generated.  False by default.
     183             :    */
     184             :   bool _smooth_after_generating;
     185             : 
     186             :   /**
     187             :    * The exact type of tetrahedra we intend to construct
     188             :    */
     189             :   ElemType _elem_type;
     190             : 
     191             :   /**
     192             :    * Local reference to the mesh we are working with.
     193             :    */
     194             :   UnstructuredMesh & _mesh;
     195             : 
     196             :   /**
     197             :    * A pointer to a vector of meshes each defining a hole.  If this is
     198             :    * nullptr, there are no holes!
     199             :    */
     200             :   std::unique_ptr<std::vector<std::unique_ptr<UnstructuredMesh>>> _holes;
     201             : };
     202             : 
     203             : 
     204             : // ------------------------------------------------------------
     205             : // MeshTetInterface class member functions
     206             : inline
     207             : void
     208             : MeshTetInterface::set_verbosity(unsigned int v)
     209             : {
     210             :   this->_verbosity = v;
     211             : }
     212             : 
     213             : 
     214             : } // namespace libMesh
     215             : 
     216             : #endif // LIBMESH_MESH_TET_INTERFACE_H