core/collision_detection/GlueToSurface.hpp

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/*
 * Copyright (C) 2011-2026 The ESPResSo project
 *
 * This file is part of ESPResSo.
 *
 * ESPResSo is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * ESPResSo 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
#pragma once
 
#include <config/config.hpp>
 
#ifdef ESPRESSO_COLLISION_DETECTION
#ifdef ESPRESSO_VIRTUAL_SITES_RELATIVE
 
#include "CollisionPair.hpp"
#include "common.hpp"
 
#include "Particle.hpp"
#include "system/System.hpp"
 
#include <vector>
 
namespace CollisionDetection {
 
class GlueToSurface {
public:
  /// Distance at which particle are bound
  double distance;
  /// Square of distance at which particle are bound
  double distance_sq;
  /// bond type used between centers of colliding particles
  int bond_centers;
  /// bond type used between virtual sites
  int bond_vs;
  /// particle type for virtual sites created on collision
  int part_type_vs;
  /// Distance from the particle which is to be glued to the new virtual site
  double dist_glued_part_to_vs;
  /// The particle type being glued (the small particle)
  int part_type_to_be_glued;
  /// The particle type to which virtual sites are attached (the large particle)
  int part_type_to_attach_vs_to;
  /// Particle type to which the newly glued particle is converted
  int part_type_after_glueing;
 
  GlueToSurface(double distance, int bond_centers, int bond_vs,
                int part_type_vs, double dist_glued_part_to_vs,
                int part_type_to_be_glued, int part_type_to_attach_vs_to,
                int part_type_after_glueing)
      : distance{distance}, distance_sq{distance * distance},
        bond_centers{bond_centers}, bond_vs{bond_vs},
        part_type_vs{part_type_vs},
        dist_glued_part_to_vs{dist_glued_part_to_vs},
        part_type_to_be_glued{part_type_to_be_glued},
        part_type_to_attach_vs_to{part_type_to_attach_vs_to},
        part_type_after_glueing{part_type_after_glueing} {}
 
  void initialize(System::System &system);
 
  auto cutoff() const { return distance; }
 
  /** @brief Check additional criteria for the glue_to_surface collision mode */
  bool glue_to_surface_criterion(Particle const &p1, Particle const &p2) const {
    return ((p1.type() == part_type_to_be_glued and
             p2.type() == part_type_to_attach_vs_to) or
            (p2.type() == part_type_to_be_glued and
             p1.type() == part_type_to_attach_vs_to));
  }
 
  void handle_collisions(System::System &system,
                         std::vector<CollisionPair> &local_collision_queue);
 
  bool detect_collision(Particle const &p1, Particle const &p2,
                        double const dist_sq) const {
    if (dist_sq > distance_sq)
      return false;
 
    if (!glue_to_surface_criterion(p1, p2))
      return false;
 
    return detect_collision_common(p1, p2, bond_centers);
  }
};
 
} // namespace CollisionDetection
#endif // ESPRESSO_VIRTUAL_SITES_RELATIVE
#endif // ESPRESSO_COLLISION_DETECTION