// Copyright (c) 2005,2006,2007,2009,2010,2011 Tel-Aviv University (Israel). // All rights reserved. // // This file is part of CGAL (www.cgal.org). // // $URL: https://github.com/CGAL/cgal/blob/v5.1/Surface_sweep_2/include/CGAL/Surface_sweep_2.h $ // $Id: Surface_sweep_2.h 4158542 2020-04-01T12:31:51+03:00 Efi Fogel // SPDX-License-Identifier: GPL-3.0-or-later OR LicenseRef-Commercial // // Author(s) : Baruch Zukerman // Efi Fogel // (based on old version by Tali Zvi) #ifndef CGAL_SURFACE_SWEEP_2_H #define CGAL_SURFACE_SWEEP_2_H #include /*! \file * * Definition of the Surface_sweep_2 class. */ #include #include #include #include #include #include #include namespace CGAL { namespace Surface_sweep_2 { /*! \class * * Surface_sweep_2 is a class that implements the sweep line algorithm based * on the algorithm of Bentley and Ottmann. * It extends the algorithm to support not only segments but general x-monotone * curves as well and isolated points. * The X_monotone_curve_2 type and Point_2 are defined by the traits class that * is one of the template arguments. * * The algorithm is also extended to support the following degenerate cases: * - vertical segments * - multiple (more then two) curves intersecting at one point * - curves beginning and ending on other curves. * - overlapping curves * * General flow: * After the initialization stage, the events are handled from left to right. * * For each event * * First pass - handles special cases in which curves start or end * at the interior of another curve * Handle left curves - iterate over the curves that intersect * at the event point and defined lexicographically to the left * of the event. * Handle right curves - iterate over the curves that intersect * the event point and defined lexicographically to the right * of the event point. This is where new intersection points * are calculated. * End * * Convensions through out the code: * In order to make the code as readable as possible, some convensions were * made in regards to variable naming: * * xp - is the intersection point between two curves * slIter - an iterator to the status line, always points to a curve. * */ template class Surface_sweep_2 : public No_intersection_surface_sweep_2 { public: typedef Visitor_ Visitor; private: typedef No_intersection_surface_sweep_2 Base; public: typedef typename Base::Geometry_traits_2 Geometry_traits_2; typedef typename Base::Event Event; typedef typename Base::Subcurve Subcurve; typedef typename Base::Allocator Allocator; typedef typename Base::Traits_adaptor_2 Traits_adaptor_2; typedef typename Traits_adaptor_2::Point_2 Point_2; typedef typename Traits_adaptor_2::X_monotone_curve_2 X_monotone_curve_2; typedef typename Traits_adaptor_2::Multiplicity Multiplicity; typedef typename Base::Event_queue_iterator Event_queue_iterator; typedef typename Event::Subcurve_iterator Event_subcurve_iterator; typedef typename Event::Attribute Attribute; typedef std::list Subcurve_container; typedef typename Subcurve_container::iterator Subcurve_iterator; typedef typename Base::Status_line_iterator Status_line_iterator; typedef CGAL::Surface_sweep_2::Curve_pair Curve_pair; typedef boost::hash Curve_pair_hasher; typedef CGAL::Surface_sweep_2::Equal_curve_pair Equal_curve_pair; typedef boost::unordered_set Curve_pair_set; typedef std::pair Intersection_point; typedef boost::variant Intersection_result; typedef std::vector Intersection_vector; typedef random_access_input_iterator vector_inserter; typedef typename Base::Subcurve_alloc Subcurve_alloc; protected: // Data members: Subcurve_container m_overlap_subCurves; // Contains all of the new sub-curves // creaed by an overlap. Curve_pair_set m_curves_pair_set; // A lookup table of pairs of Subcurves // that have been intersected. Intersection_vector m_x_objects; // Auxiliary vector for storing the // intersection objects. X_monotone_curve_2 sub_cv1; // Auxiliary varibales X_monotone_curve_2 sub_cv2; // (for splitting curves). public: /*! Constructor. * \param visitor A pointer to a sweep-line visitor object. */ Surface_sweep_2(Visitor* visitor) : Base(visitor), m_curves_pair_set(0) {} /*! * Construct. * \param traits A pointer to a sweep-line traits object. * \param visitor A pointer to a sweep-line visitor object. */ Surface_sweep_2(const Geometry_traits_2* traits, Visitor* visitor) : Base(traits, visitor), m_curves_pair_set(0) {} /*! Destrcut. */ virtual ~Surface_sweep_2() {} protected: typedef typename std::vector Subcurve_vector; /*! Initialize the data structures for the sweep-line algorithm. */ virtual void _init_structures(); /*! Complete the sweep process (complete the data structures). */ virtual void _complete_sweep(); /*! Handle the subcurves to the left of the current event point. */ virtual void _handle_left_curves(); /*! Handle the overlap on the right curves of the current event point. */ void _handle_overlaps_in_right_curves(); /*! clip the last curve of a subcurve if it is not in the status line and with a left end not being the current event*/ void _clip_non_active_curve_at_current_event(Subcurve*); /*! Handle the subcurves to the right of the current event point. */ virtual void _handle_right_curves(); /*! Add a subcurve to the right of an event point. * \param event The event point. * \param curve The subcurve to add. */ virtual bool _add_curve_to_right(Event* event, Subcurve* curve); /*! Add a curve as a right curve or left curve when the event is created * or updated. */ void _add_curve(Event* e, Subcurve* sc, Attribute type); /*! create an overlap subcurve from overlap_cv between c1 and c2. * \param overlap_cv the overlapping curve. * \param c1 first subcurve contributing to the overlap. * \param c2 second subcurve contributing to the overlap. * \param all_leaves_diff not empty in case c1 and c2 have common ancesters. * It contains the set of curves not contained in first_parent * that are in the other subcurve * \param first_parent only used when c1 and c2 have common ancesters. * It is either c1 or c2 (the one having the more leaves) * */ void _create_overlapping_curve(const X_monotone_curve_2& overlap_cv, Subcurve*& c1 , Subcurve*& c2, const Subcurve_vector& all_leaves_diff, Subcurve* first_parent, Event* event_on_overlap); /*! Compute intersections between the two given curves. * If the two curves intersect, create a new event (or use the event that * already exits in the intersection point) and insert the curves to the * event. * \param curve1 The first curve. * \param curve2 The second curve. */ void _intersect(Subcurve* c1, Subcurve* c2, Event* event_for_overlap = nullptr); /*! When a curve is removed from the status line for good, its top and * bottom neighbors become neighbors. This method finds these cases and * looks for the intersection point, if one exists. * \param leftCurve A pointer to the curve that is about to be deleted. * \param remove_for_good Whether the aubcurve is removed for good. */ void _remove_curve_from_status_line(Subcurve* leftCurve, bool remove_for_good); /*! Create an intersection-point event between two curves. * \param xp The intersection point. * \param mult Its multiplicity. * \param curve1 The first curve. * \param curve2 The second curve. */ void _create_intersection_point(const Point_2& xp, unsigned int mult, Subcurve*& c1, Subcurve*& c2); }; } // namespace Surface_sweep_2 } // namespace CGAL // The member-function definitions can be found in: #include #endif