inter_mesh_projection.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_INTER_MESH_PROJECTION_H
#define LIBMESH_INTER_MESH_PROJECTION_H

// Local includes
#include "libmesh/libmesh.h"
#include "libmesh/mesh.h"
#include "libmesh/system.h"
#include "libmesh/equation_systems.h"
#include "libmesh/mesh_function.h"
#include "libmesh/numeric_vector.h"
#include "libmesh/numeric_vector.h"
#include "libmesh/fem_function_base.h"

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

namespace libMesh
{

// Forward declarations

class InterMeshProjection
{
public:

  // Constructor, specifies the _from_system whose vectors will be
  // projected onto the _to_mesh
  InterMeshProjection(System & _from_system, System & _to_mesh);

  // Projects from_system vectors onto the to_mesh
  void project_system_vectors();

  static Number fptr(const Point & p, const Parameters &, const std::string & libmesh_dbg_var(sys_name), const std::string & unknown_name);

  static Gradient gptr(const Point & p, const Parameters &, const std::string & libmesh_dbg_var(sys_name), const std::string & unknown_name);

private:

  // Local copy of the _from_system
  System & from_system;

  // Local copy of the _to_system
  System & to_system;

};

// This class provides the functor we will supply to System::project_vector
// inside InterMeshProjection::project_system_vectors.
// Object is constructed by passing in a pointer to the mesh function whose
// gradient we want to shim via operator().
class GradientMeshFunction : public FunctionBase<Gradient>
{
public:
  // Constructor
  GradientMeshFunction(const MeshFunction & _mesh_function);

  // Destructor
  virtual ~GradientMeshFunction () { }

  virtual void init () { }

  virtual std::unique_ptr<FunctionBase<Gradient>> clone () const
  {
    return std::make_unique<GradientMeshFunction>(*mesh_function);
  }

  virtual Gradient operator() (const Point & , const Real)
  { libmesh_not_implemented(); }

  virtual void operator() (const Point & p, const Real, DenseVector<Gradient> & output);

private:

  // Local copy of the passed in mesh function.
  std::unique_ptr<MeshFunction> mesh_function;

};
}

#endif // LIBMESH_INTER_MESH_PROJECTION_H