// Copyright (c) 1997-2002 Max-Planck-Institute Saarbruecken (Germany). // All rights reserved. // // This file is part of CGAL (www.cgal.org). // // $URL: https://github.com/CGAL/cgal/blob/v5.1/Nef_S2/include/CGAL/Nef_S2/Sphere_segment.h $ // $Id: Sphere_segment.h 0779373 2020-03-26T13:31:46+01:00 Sébastien Loriot // SPDX-License-Identifier: GPL-3.0-or-later OR LicenseRef-Commercial // // // Author(s) : Michael Seel #ifndef CGAL_SPHERE_SEGMENT_H #define CGAL_SPHERE_SEGMENT_H #include #include #include #include namespace CGAL { template class Sphere_segment_rep { typedef typename R_::Point_3 Point_3; typedef typename R_::Plane_3 Plane_3; typedef Sphere_point Point; typedef Sphere_circle Circle; typedef Sphere_segment_rep Rep; friend class Sphere_segment; public: Sphere_segment_rep() { ps_ = pt_ = Point(); c_ = Circle(); } Sphere_segment_rep(const Point& p1, const Point& p2, bool shorter_arc=true) : ps_(p1), pt_(p2), c_(Plane_3(p1,p2,Point_3(0,0,0))) { // warning stays as reminder that one gets an arbitrary plane equation // in this degenerate case CGAL_warning(p1 != p2.antipode()); CGAL_assertion(p1 != p2.antipode()); if ( p1 == p2 ) { Plane_3 h(Point_3(0,0,0),(p1-CGAL::ORIGIN)); c_ = Sphere_circle(Plane_3(Point_3(0,0,0),h.base1())); } if (!shorter_arc) c_ = c_.opposite(); CGAL_exactness_assertion(c_.has_on(p1) && c_.has_on(p2)); } Sphere_segment_rep(const Point& p1, const Point& p2, const Circle& c) : ps_(p1), pt_(p2), c_(c) { CGAL_assertion(c.has_on(p1)&&c.has_on(p2)); } Sphere_segment_rep(const Circle& c1, const Circle& c2) : c_(c1) { CGAL_assertion(!equal_as_sets(c1,c2)); ps_ = intersection(c1,c2); pt_ = ps_.antipode(); if ( R_::orientation(Point_3(0,0,0),ps_,pt_, CGAL::ORIGIN + c_.orthogonal_vector()) != CGAL::POSITIVE ) std::swap(ps_,pt_); } Sphere_segment_rep(const Rep& r) : ps_(r.ps_), pt_(r.pt_), c_(r.c_) {} Rep& operator=(const Rep& r) { ps_=r.ps_; pt_=r.pt_; c_=r.c_; return *this; } protected: Sphere_point ps_,pt_; Sphere_circle c_; }; /*{\Moptions print_title=yes }*/ /*{\Manpage{Sphere_segment}{R}{Segments on the unit sphere}{s}}*/ template class Sphere_segment : public Handle_for< Sphere_segment_rep > { /*{\Mdefinition An object |\Mvar| of type |\Mname| is a segment in the surface of a unit sphere that is part of a great circle trough the origin. Sphere segments are represented by two sphere points $p$ and $q$ plus an oriented plane $h$ that contains $p$ and $q$. The plane determines the sphere segment. Let $c$ be the circle in the intersection of $h$ and $S_2$. Then $s$ is that part of $c$ that is swept, when we rotate $p$ into $q$ in counterclockwise rotation around the normal vector of $h$ as seen from the positive halfspace.}*/ public: /*{\Mtypes 6}*/ typedef R_ R; /*{\Mtypemember representation class.}*/ typedef typename R_::RT RT; /*{\Mtypemember ring number type.}*/ typedef Sphere_segment_rep Rep; typedef Handle_for Base; typedef typename R_::Point_3 Point_3; typedef typename R_::Vector_3 Vector_3; typedef typename R_::Plane_3 Plane_3; typedef typename R_::Line_3 Line_3; typedef Sphere_segment Self; /*{\Mcreation 4}*/ Sphere_segment() : Base() {} Sphere_segment(const Sphere_point& p1, const Sphere_point& p2, bool shorter_arc=true) : Base(Rep(p1,p2,shorter_arc)) {} /*{\Mcreate creates a spherical segment spanning the shorter arc from |p1| to |p2| if |shorter_arc == true|. Otherwise the longer arc is created. \precond |p1 != p2| and |p1 != p2.antipode()|.}*/ Sphere_segment(const Sphere_point& p1, const Sphere_point& p2, const Sphere_circle& c) : Base(Rep(p1,p2,c)) {} /*{\Mcreate creates a spherical segment spanning the arc from |p1| to |p2| as part of the oriented circle |c| (|p1 == p2| or |p1 == p2.antipode()| are possible.) \precond |p1| and |p2| are contained in |c|.}*/ Sphere_segment(const Sphere_circle& c1, const Sphere_circle& c2) : Base(Rep(c1,c2)) {} /*{\Mcreate creates the spherical segment as part of |c1| that is part of the halfsphere left of the oriented circle |c2|. \precond |c1 != c2| as unoriented circles.}*/ // Sphere_segment(const Self& s) : Base(s) {} /*{\Moperations 4 2}*/ const Sphere_point& source() const { return this->ptr()->ps_; } /*{\Mop the source point of |\Mvar|.}*/ const Sphere_point& target() const { return this->ptr()->pt_; } /*{\Mop the target point of |\Mvar|.}*/ const Sphere_circle& sphere_circle() const { return this->ptr()->c_; } /*{\Mop the great circle supporting |\Mvar|.}*/ Sphere_segment opposite() const /*{\Mop returns the sperical segment oriented from |target()| to |source()| with the same point set as |\Mvar|. }*/ { return Sphere_segment( target(),source(),sphere_circle().opposite()); } Sphere_segment complement() const /*{\Mop returns the sperical segment oriented from |target()| to |source()| with the point set completing |\Mvar| to a full circle. }*/ { return Sphere_segment(target(),source(),sphere_circle()); } int intersection(const Sphere_circle& c, std::vector >& s) const; int intersection(const Sphere_circle& c, Sphere_segment& s1, Sphere_segment& s2) const; /*{\Mop returns the number of non-trivial connected components of the intersection of |\Mvar| and the closed halfsphere left of |c|.}*/ Sphere_point intersection(const Sphere_segment& so) const; /*{\Mop returns the point of intersection of |\Mvar| and |so|. \precond |\Mvar| and |so| do intersect.}*/ void split_halfcircle(Sphere_segment& s1, Sphere_segment& s2) const /*{\Mop splits a halfcircle into two equally sized segments. \precond |\Mvar| is a halfcircle.}*/ { CGAL_assertion( is_halfcircle() ); Plane_3 h(Point_3(0,0,0),(target()-CGAL::ORIGIN)); Sphere_point p = CGAL::intersection(sphere_circle(),Sphere_circle(h)); if ( !has_on(p) ) p = p.antipode(); s1 = Sphere_segment(this->ptr()->ps_,p,this->ptr()->c_); s2 = Sphere_segment(p,this->ptr()->pt_,this->ptr()->c_); } bool is_short() const /*{\Mop a segment is short iff it is shorter than a halfcircle.}*/ { return R().orientation_3_object()(Point_3(0,0,0), Point_3(source()), Point_3(target()), CGAL::ORIGIN + this->ptr()->c_.orthogonal_vector()) == CGAL::POSITIVE; } bool is_long() const /*{\Mop a segment is long iff it is longer than a halfcircle.}*/ { return R().orientation_3_object()(Point_3(0,0,0), Point_3(source()), Point_3(target()), CGAL::ORIGIN + this->ptr()->c_.orthogonal_vector()) == CGAL::NEGATIVE; } bool is_degenerate() const { return source() == target(); } /*{\Mop return true iff |\Mvar| is degenerate.}*/ bool is_halfcircle() const { return source().antipode() == target(); } /*{\Mop return true iff |\Mvar| is a halfcircle.}*/ bool has_on(const Sphere_point& p) const; /*{\Mop return true iff |\Mvar| contains |p|.}*/ bool has_on_after_intersection(const Sphere_point& p) const; bool has_in_relative_interior(const Sphere_point& p) const; /*{\Mop return true iff |\Mvar| contains |p| in its relative interior.}*/ bool operator==(const Sphere_segment& so) const { return source() == so.source() && target() == so.target() && (source() == target() || sphere_circle() == so.sphere_circle()); } bool operator!=(const Sphere_segment& so) const { return !operator==(so); } }; template bool do_intersect_internally(const Sphere_segment& s1, const Sphere_segment& s2, Sphere_point& p); /*{\Mfunc return true iff |s1| and |s2| intersect internally (non-degenerately). If |true| the parameter |p| returns the point of intersection.}*/ template std::ostream& operator<<(std::ostream& os, const CGAL::Sphere_segment& s) { os << s.source()<<" "< std::istream& operator>>(std::istream& is, CGAL::Sphere_segment& s) { CGAL::Sphere_point p1,p2; CGAL::Sphere_circle c; if ( !(is >> p1 >> p2 >> c) ) return is; s = CGAL::Sphere_segment(p1,p2,c); return is; } template std::pair< Sphere_segment,Sphere_segment > Sphere_circle::split_at(const Sphere_point& p) const { CGAL_assertion(has_on(p)); Sphere_point q(p.antipode()); return Sphere_segment_pair( Sphere_segment(p,q,*this), Sphere_segment(p,q,this->opposite())); } template std::pair< Sphere_segment,Sphere_segment > Sphere_circle::split_at_xy_plane() const { Self xycircle(0,0,1), yzcircle(1,0,0); if ( !equal_as_sets(xycircle,*this) ) return split_at(intersection(*this,xycircle)); else return split_at(intersection(*this,yzcircle)); } /* Contains maps to two orientation checks with the wedge spanned by the source and the target with planes orthogonal to the supporting plane of $p$ and $q$. The logic depends on the segments length: long or short. */ template bool Sphere_segment:: has_on(const CGAL::Sphere_point& p) const { if ( !sphere_circle().has_on(p) ) return false; if ( !is_long() ) { return orientation(Point_3(0,0,0), CGAL::ORIGIN + sphere_circle().orthogonal_vector(), source(),p) != CGAL::NEGATIVE && orientation(Point_3(0,0,0),target(), CGAL::ORIGIN + sphere_circle().orthogonal_vector(),p) != CGAL::NEGATIVE; } else { return orientation(Point_3(0,0,0), CGAL::ORIGIN + sphere_circle().orthogonal_vector(), source(),p) != CGAL::NEGATIVE || orientation(Point_3(0,0,0),target(), CGAL::ORIGIN + sphere_circle().orthogonal_vector(),p) != CGAL::NEGATIVE; } } template bool Sphere_segment:: has_on_after_intersection(const CGAL::Sphere_point& p) const { return orientation(Point_3(0,0,0), CGAL::ORIGIN + sphere_circle().orthogonal_vector(), source(),p) != CGAL::NEGATIVE && orientation(Point_3(0,0,0),target(), CGAL::ORIGIN + sphere_circle().orthogonal_vector(),p) != CGAL::NEGATIVE; } template bool Sphere_segment:: has_in_relative_interior(const CGAL::Sphere_point& p) const { if ( !sphere_circle().has_on(p) ) return false; if ( !is_long() ) { return orientation(Point_3(0,0,0), CGAL::ORIGIN + sphere_circle().orthogonal_vector(), source(),p) == CGAL::POSITIVE && orientation(Point_3(0,0,0),target(), CGAL::ORIGIN + sphere_circle().orthogonal_vector(),p) == CGAL::POSITIVE; } else { return orientation(Point_3(0,0,0), CGAL::ORIGIN + sphere_circle().orthogonal_vector(), source(),p) == CGAL::POSITIVE || orientation(Point_3(0,0,0),target(), CGAL::ORIGIN + sphere_circle().orthogonal_vector(),p) == CGAL::POSITIVE; } } /* Intersection of two sphere segments. It does not work if the two involved planes are equal as sets. */ template Sphere_point Sphere_segment:: intersection(const Sphere_segment& s) const { CGAL_assertion(!equal_as_sets(sphere_circle(),s.sphere_circle())); Sphere_point res = CGAL::intersection(sphere_circle(),s.sphere_circle()); if ( has_on(res) && s.has_on(res) ) return res; return res.antipode(); } template bool do_intersect_internally(const Sphere_segment& s1, const Sphere_segment& s2, Sphere_point& p) { if ( equal_as_sets(s1.sphere_circle(),s2.sphere_circle()) ) return false; p = CGAL::intersection(s1.sphere_circle(),s2.sphere_circle()); if ( s1.has_in_relative_interior(p) && s2.has_in_relative_interior(p) ) return true; p = p.antipode(); if ( s1.has_in_relative_interior(p) && s2.has_in_relative_interior(p) ) return true; return false; } template bool do_intersect_internally(const Sphere_circle& c1, const Sphere_segment& s2, Sphere_point& p) { if ( equal_as_sets(c1,s2.sphere_circle()) ) return false; p = CGAL::intersection(c1,s2.sphere_circle()); if ( s2.has_in_relative_interior(p) ) return true; p = p.antipode(); if ( s2.has_in_relative_interior(p) ) return true; return false; } } //namespace CGAL #endif //CGAL_SPHERE_SEGMENT_H