/usr/include/CGAL/Parabola_2.h is in libcgal-dev 4.7-4.
This file is owned by root:root, with mode 0o644.
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// All rights reserved.
//
// This file is part of CGAL (www.cgal.org).
// 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.
//
// Licensees holding a valid commercial license may use this file in
// accordance with the commercial license agreement provided with the software.
//
// This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
// WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
//
// $URL$
// $Id$
//
//
// Author(s) : Menelaos Karavelas <mkaravel@iacm.forth.gr>
#ifndef CGAL_PARABOLA_2_H
#define CGAL_PARABOLA_2_H
#include <vector>
#include <CGAL/determinant.h>
#include <CGAL/Algebraic_structure_traits.h>
#include <CGAL/number_utils.h>
namespace CGAL {
template < class Gt >
class Parabola_2
{
private:
typedef Parabola_2<Gt> Self;
public:
typedef typename Gt::Site_2 Site_2;
typedef typename Gt::Point_2 Point_2;
typedef typename Gt::Segment_2 Segment_2;
typedef typename Gt::Line_2 Line_2;
typedef typename Gt::FT FT;
// typedef CGAL::Point_2< Cartesian<double> > Point_2;
// typedef CGAL::Segment_2< Cartesian<double> > Segment_2;
// typedef CGAL::Line_2< Cartesian<double> > Line_2;
private:
typedef Algebraic_structure_traits<FT> AST;
protected:
// static stuff
#if defined(__POWERPC__) && \
defined(__GNUC__) && (__GNUC__ == 3) && (__GNUC_MINOR__ == 4)
// hack to avoid nasty warning for G++ 3.4 on Darwin
static FT STEP()
{
return FT(2);
}
#else
static const FT& STEP()
{
static FT step_(2);
return step_;
}
#endif
// inline static
// FT square(const FT &x)
// {
// return x * x;
// }
inline static
FT divide(const FT& x, const FT& y) {
return CGAL::integral_division(x,y);
}
inline static
FT sqrt(const FT& x, Integral_domain_without_division_tag) {
return CGAL::sqrt(CGAL::to_double(x));
}
inline static
FT sqrt(const FT& x, Field_with_sqrt_tag) {
return CGAL::sqrt(x);
}
inline static
FT sqrt(const FT& x) {
return sqrt(x, typename AST::Algebraic_category());
}
inline static
FT norm2(const Point_2& p)
{
return CGAL::square(p.x()) + CGAL::square(p.y());
}
inline static
FT distance2(const Point_2& p1, const Point_2& p2)
{
FT dx = p1.x()-p2.x();
FT dy = p1.y()-p2.y();
return CGAL::square(dx) + CGAL::square(dy);
}
inline static
FT distance(const Point_2& p1, const Point_2& p2)
{
return sqrt( distance2(p1, p2) );
}
inline static
FT distance(const Point_2& p, const Line_2& l)
{
return divide( p.x() * l.a() + p.y() * l.b() + l.c(),
sqrt( CGAL::square(l.a()) + CGAL::square(l.b()) ) );
}
// instance stuff
Point_2 c;
Line_2 l;
Point_2 o;
inline
Point_2 lchain(const FT &t) const
{
std::vector< Point_2 > p = compute_points(t);
if ( right(p[0]) ) return p[1];
return p[0];
}
inline
Point_2 rchain(const FT &t) const
{
std::vector< Point_2 > p = compute_points(t);
if ( right(p[0]) ) return p[0];
return p[1];
}
std::vector< Point_2 > compute_points(const FT &d) const
{
CGAL_assertion(d >= 0);
FT d1 = distance(o, c) + d;
FT d2 = distance(o, l) + d;
d2 = d1;
d1 *= d1;
std::vector< Point_2 > p;
if ( l.a() == ZERO ) {
FT y = d2 * CGAL::sign(l.b()) - divide(l.c(), l.b());
FT C = CGAL::square(y) - FT(2) * c.y() * y +
CGAL::square(c.x()) + CGAL::square(c.y()) - d1;
FT D = CGAL::square(c.x()) - C;
D = CGAL::abs(D);
FT x1 = sqrt(D) + c.x();
FT x2 = -sqrt(D) + c.x();
p.push_back(Point_2(x1, y));
p.push_back(Point_2(x2, y));
return p;
}
FT A = d2 * sqrt( CGAL::square(l.a()) + CGAL::square(l.b()) ) - l.c();
FT B = CGAL::square(c.x()) + CGAL::square(c.y()) - d1;
FT alpha = FT(1) + CGAL::square(divide(l.b(), l.a()));
FT beta = divide(A * l.b(), CGAL::square(l.a())) + c.y()
- divide(c.x() * l.b(), l.a());
FT gamma = CGAL::square(divide(A, l.a())) + B
- divide(FT(2) * c.x() * A, l.a());
FT D = CGAL::square(beta) - alpha * gamma;
D = CGAL::abs(D);
FT y1 = divide((beta + sqrt(D)), alpha);
FT y2 = divide((beta - sqrt(D)), alpha);
FT x1 = divide(A - l.b() * y1, l.a());
FT x2 = divide(A - l.b() * y2, l.a());
p.push_back(Point_2(x1, y1));
p.push_back(Point_2(x2, y2));
return p;
}
bool right(const Point_2& p) const
{
return
CGAL::is_positive( determinant<FT>(c.x(), c.y(), FT(1),
o.x(), o.y(), FT(1),
p.x(), p.y(), FT(1)) );
}
inline
Point_2 midpoint(const Point_2& p1, const Point_2& p2) const
{
FT t1 = t(p1);
FT t2 = t(p2);
FT midt = divide(t1+t2, FT(2));
return f(midt);
}
inline
Point_2 f(FT t) const
{
if ( CGAL::is_negative(t) ) return rchain(-t);
return lchain(t);
}
inline
FT t(const Point_2 &p) const
{
FT tt = distance(p, c) - distance(c, o);
if ( right(p) ) return -tt;
return tt;
}
void compute_origin()
{
FT d = divide(l.a() * c.x() + l.b() * c.y() + l.c(),
FT(2) * ( CGAL::square(l.a()) + CGAL::square(l.b()) ) );
o = Point_2(c.x() - l.a() * d, c.y() - l.b() * d);
}
public:
Parabola_2() {}
template<class ApolloniusSite>
Parabola_2(const ApolloniusSite &p, const Line_2 &l1)
{
this->c = p.point();
FT d_a = CGAL::to_double(l1.a());
FT d_b = CGAL::to_double(l1.b());
FT len = sqrt(CGAL::square(d_a) + CGAL::square(d_b));
FT r = p.weight() * len;
this->l = Line_2(-l1.a(), -l1.b(), -l1.c() + r);
compute_origin();
}
Parabola_2(const Point_2 &p, const Line_2 &line)
{
this->c = p;
if ( line.has_on_positive_side(p) ) {
this->l = line;
} else {
this->l = line.opposite();
}
compute_origin();
}
Oriented_side
side_of_parabola(const Point_2& p) const
{
Point_2 q(CGAL::to_double(p.x()), CGAL::to_double(p.y()));
FT d = distance(q, c) - CGAL::abs(distance(q, l));
if ( d < 0 ) return ON_NEGATIVE_SIDE;
if ( d > 0 ) return ON_POSITIVE_SIDE;
return ON_ORIENTED_BOUNDARY;
}
inline Line_2 line() const
{
return l;
}
inline Point_2 center() const
{
return c;
}
template< class Stream >
void draw(Stream& W) const
{
std::vector< Point_2 > p;
std::vector< Point_2 > pleft, pright;
pleft.push_back(o);
pright.push_back(o);
for (int i = 1; i <= 100; i++) {
p = compute_points(i * i * STEP());
W << p[0];
W << p[1];
if ( p.size() > 0 ) {
if ( right(p[0]) ) {
pright.push_back(p[0]);
pleft.push_back(p[1]);
} else {
pright.push_back(p[1]);
pleft.push_back(p[0]);
}
}
}
for (unsigned int i = 0; i < pleft.size() - 1; i++) {
W << Segment_2(pleft[i], pleft[i+1]);
}
for (unsigned int i = 0; i < pright.size() - 1; i++) {
W << Segment_2(pright[i], pright[i+1]);
}
W << o;
}
};
template< class Stream, class Gt >
inline
Stream& operator<<(Stream& s, const Parabola_2<Gt> &P)
{
P.draw(s);
return s;
}
} //namespace CGAL
#endif // CGAL_PARABOLA_2_H
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