triangulator_interface.h

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// The libMesh Finite Element Library.
// Copyright (C) 2002-2025 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_MESH_TRIANGULATOR_INTERFACE_H
#define LIBMESH_MESH_TRIANGULATOR_INTERFACE_H


#include "libmesh/libmesh_config.h"

// Local Includes
#include "libmesh/libmesh.h"
#include "libmesh/point.h"

#include "libmesh/function_base.h"

// C++ includes
#include <set>
#include <vector>

namespace libMesh
{

// Forward Declarations
class UnstructuredMesh;
template <unsigned int KDDim>
class InverseDistanceInterpolation;
enum ElemType : int;

// Helper function for auto area calculation
class AutoAreaFunction : public FunctionBase<Real>
{
public:
  AutoAreaFunction (const Parallel::Communicator &comm,
                    const unsigned int num_nearest_pts,
                    const unsigned int power,
                    const Real background_value,
                    const Real  background_eff_dist);

  AutoAreaFunction (const AutoAreaFunction &);
  AutoAreaFunction & operator= (const AutoAreaFunction &);

  AutoAreaFunction (AutoAreaFunction &&) = delete;
  AutoAreaFunction & operator= (AutoAreaFunction &&) = delete;
  virtual ~AutoAreaFunction ();

  void init_mfi (const std::vector<Point> & input_pts,
                 const std::vector<Real> & input_vals);

  virtual Real operator() (const Point & p,
                           const Real /*time*/) override;

  virtual void operator() (const Point & p,
                           const Real time,
                           DenseVector<Real> & output) override
  {
    output.resize(1);
    output(0) = (*this)(p,time);
    return;
  }

  virtual std::unique_ptr<FunctionBase<Real>> clone() const override
  {
    return std::make_unique<AutoAreaFunction>(_comm, _num_nearest_pts, _power, _background_value, _background_eff_dist);
  }

private:
  const Parallel::Communicator & _comm;
  const unsigned int _num_nearest_pts;
  const unsigned int _power;
  const Real _background_value;
  const Real _background_eff_dist;
  std::unique_ptr<InverseDistanceInterpolation<3>> _auto_area_mfi;
};

class TriangulatorInterface
{
public:
  explicit
  TriangulatorInterface(UnstructuredMesh & mesh);

  virtual ~TriangulatorInterface() = default;

  enum TriangulationType
    {
      GENERATE_CONVEX_HULL = 0,

      PSLG = 1,

      INVALID_TRIANGULATION_TYPE
    };

  class Hole;
  class AffineHole;
  class PolygonHole;
  class ArbitraryHole;
  class MeshedHole;

  class Region;

  virtual void triangulate() = 0;

  ElemType & elem_type() {return _elem_type;}

  Real & desired_area() {return _desired_area;}

  virtual void set_desired_area_function (FunctionBase<Real> *)
  { libmesh_not_implemented(); }

  virtual FunctionBase<Real> * get_desired_area_function ()
  { return nullptr; }

  Real & minimum_angle() {return _minimum_angle;}

  TriangulationType & triangulation_type() {return _triangulation_type;}

  bool & insert_extra_points() {return _insert_extra_points;}

  void set_interpolate_boundary_points (int n_points);

  int get_interpolate_boundary_points () const;

  virtual void set_refine_boundary_allowed (bool)
  { libmesh_not_implemented(); }

  virtual bool refine_boundary_allowed () const
  { return true; }

  bool & smooth_after_generating() {return _smooth_after_generating;}

  bool & quiet() {return _quiet;}

  void attach_hole_list(const std::vector<Hole*> * holes) {_holes = holes;}

  void set_verify_hole_boundaries(bool v) {_verify_hole_boundaries = v;}

  bool get_verify_hole_boundaries() const {return _verify_hole_boundaries;}

  std::vector<std::pair<unsigned int, unsigned int>> segments;

  std::vector<Point> segment_midpoints;

  void attach_boundary_marker(const std::vector<int> * markers) { _markers = markers; }

  void attach_region_list(const std::vector<Region*> * regions) { _regions = regions; }

  void set_auto_area_function(const Parallel::Communicator &comm,
                              const unsigned int num_nearest_pts,
                              const unsigned int power,
                              const Real background_value,
                              const Real  background_eff_dist);

  bool has_auto_area_function() {return _auto_area_function != nullptr;}

  FunctionBase<Real> * get_auto_area_function ();

  void calculate_auto_desired_area_samples(std::vector<Point> & function_points,
                                           std::vector<Real> & function_sizes,
                                           const Real & area_factor = 1.5);

  void set_outer_boundary_ids(std::set<std::size_t> bdy_ids) { _bdy_ids = std::move(bdy_ids); }
  const std::set<std::size_t> & get_outer_boundary_ids() const { return _bdy_ids; }

protected:
  void elems_to_segments();

  void nodes_to_segments(dof_id_type max_node_id);

  void insert_any_extra_boundary_points();

  void increase_triangle_order();

  void verify_holes(const Hole & outer_bdy);

  unsigned int total_hole_points();

  UnstructuredMesh & _mesh;

  const std::vector<Hole*> * _holes;

  const std::vector<int> * _markers;

  const std::vector<Region*> * _regions;

  std::set<std::size_t> _bdy_ids;

  ElemType _elem_type;

  Real _desired_area;

  Real _minimum_angle;

  TriangulationType _triangulation_type;

  bool _insert_extra_points;

  int _interpolate_boundary_points;

  bool _smooth_after_generating;

  bool _quiet;

  bool _verify_hole_boundaries;

  std::unique_ptr<AutoAreaFunction> _auto_area_function;
};

} // namespace libMesh

#endif // ifndef LIBMESH_MESH_TRIANGULATOR_INTERFACE_H