conicsec.h revision 76addc201c409e81eaaa73fe27cc0f79c4db097c
/** @file
* @brief Conic Section
*//*
* Authors:
* Nathan Hurst <njh@njhurst.com>
*
* Copyright 2009 authors
*
* This library is free software; you can redistribute it and/or
* modify it either under the terms of the GNU Lesser General Public
* License version 2.1 as published by the Free Software Foundation
* (the "LGPL") or, at your option, under the terms of the Mozilla
* Public License Version 1.1 (the "MPL"). If you do not alter this
* notice, a recipient may use your version of this file under either
* the MPL or the LGPL.
*
* You should have received a copy of the LGPL along with this library
* in the file COPYING-LGPL-2.1; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
* You should have received a copy of the MPL along with this library
* in the file COPYING-MPL-1.1
*
* The contents of this file are subject to the Mozilla Public License
* Version 1.1 (the "License"); you may not use this file except in
* compliance with the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY
* OF ANY KIND, either express or implied. See the LGPL or the MPL for
* the specific language governing rights and limitations.
*/
#ifndef LIB2GEOM_SEEN_CONICSEC_H
#define LIB2GEOM_SEEN_CONICSEC_H
#include <2geom/exception.h>
#include <2geom/angle.h>
#include <2geom/rect.h>
#include <2geom/affine.h>
#include <2geom/point.h>
#include <2geom/line.h>
#include <2geom/bezier-curve.h>
#include <2geom/numeric/linear_system.h>
#include <2geom/numeric/symmetric-matrix-fs.h>
#include <2geom/numeric/symmetric-matrix-fs-operation.h>
#include <boost/optional/optional.hpp>
#include <string>
#include <vector>
#include <ostream>
namespace Geom
{
class RatQuad{
/**
* A curve of the form B02*A + B12*B*w + B22*C/(B02 + B12*w + B22)
* These curves can exactly represent a piece conic section less than a certain angle (find out)
*
**/
public:
Point P[3];
double w;
RatQuad() {}
RatQuad(Point a, Point b, Point c, double w) : w(w) {
P[0] = a;
P[1] = b;
P[2] = c;
}
double lambda() const;
static RatQuad fromPointsTangents(Point P0, Point dP0,
Point P,
Point P2, Point dP2);
static RatQuad circularArc(Point P0, Point P1, Point P2);
CubicBezier toCubic() const;
CubicBezier toCubic(double lam) const;
Point pointAt(double t) const;
Point at0() const {return P[0];}
Point at1() const {return P[2];}
void split(RatQuad &a, RatQuad &b) const;
D2<SBasis> hermite() const;
std::vector<SBasis> homogenous() const;
};
class xAx{
public:
double c[6];
enum kind_t
{
PARABOLA,
CIRCLE,
REAL_ELLIPSE,
IMAGINARY_ELLIPSE,
RECTANGULAR_HYPERBOLA,
HYPERBOLA,
DOUBLE_LINE,
TWO_REAL_PARALLEL_LINES,
TWO_IMAGINARY_PARALLEL_LINES,
TWO_REAL_CROSSING_LINES,
TWO_IMAGINARY_CROSSING_LINES, // crossing at a real point
SINGLE_POINT = TWO_IMAGINARY_CROSSING_LINES,
UNKNOWN
};
xAx() {}
/*
* Define the conic section by its algebraic equation coefficients
*
* c0, .., c5: equation coefficients
*/
xAx (double c0, double c1, double c2, double c3, double c4, double c5)
{
set (c0, c1, c2, c3, c4, c5);
}
/*
* Define a conic section by its related symmetric matrix
*/
xAx (const NL::ConstSymmetricMatrixView<3> & C)
{
set(C);
}
/*
* Define a conic section by computing the one that fits better with
* N points.
*
* points: points to fit
*
* precondition: there must be at least 5 non-overlapping points
*/
xAx (std::vector<Point> const& points)
{
set (points);
}
/*
* Define a section conic by providing the coordinates of one of its
* vertex,the major axis inclination angle and the coordinates of its foci
* with respect to the unidimensional system defined by the major axis with
* origin set at the provided vertex.
*
* _vertex : section conic vertex V
* _angle : section conic major axis angle
* _dist1: +/-distance btw V and nearest focus
* _dist2: +/-distance btw V and farest focus
*
* prerequisite: _dist1 <= _dist2
*/
xAx (const Point& _vertex, double _angle, double _dist1, double _dist2)
{
set (_vertex, _angle, _dist1, _dist2);
}
/*
* Define a conic section by providing one of its vertex and its foci.
*
* _vertex: section conic vertex
* _focus1: section conic focus
* _focus2: section conic focus
*/
xAx (const Point& _vertex, const Point& _focus1, const Point& _focus2)
{
set(_vertex, _focus1, _focus2);
}
/*
* Define a conic section by passing a focus, the related directrix,
* and the eccentricity (e)
* (e < 1 -> ellipse; e = 1 -> parabola; e > 1 -> hyperbola)
*
* _focus: a focus of the conic section
* _directrix: the directrix related to the given focus
* _eccentricity: the eccentricity parameter of the conic section
*/
xAx (const Point & _focus, const Line & _directrix, double _eccentricity)
{
set (_focus, _directrix, _eccentricity);
}
/*
* Made up a degenerate conic section as a pair of lines
*
* l1, l2: lines that made up the conic section
*/
xAx (const Line& l1, const Line& l2)
{
set (l1, l2);
}
/*
* Define the conic section by its algebraic equation coefficients
* c0, ..., c5: equation coefficients
*/
void set (double c0, double c1, double c2, double c3, double c4, double c5)
{
c[0] = c0; c[1] = c1; c[2] = c2; // xx, xy, yy
c[3] = c3; c[4] = c4; // x, y
c[5] = c5; // 1
}
/*
* Define a conic section by its related symmetric matrix
*/
void set (const NL::ConstSymmetricMatrixView<3> & C)
{
set(C(0,0), 2*C(1,0), C(1,1), 2*C(2,0), 2*C(2,1), C(2,2));
}
void set (std::vector<Point> const& points);
void set (const Point& _vertex, double _angle, double _dist1, double _dist2);
void set (const Point& _vertex, const Point& _focus1, const Point& _focus2);
void set (const Point & _focus, const Line & _directrix, double _eccentricity);
void set (const Line& l1, const Line& l2);
static xAx fromPoint(Point p);
static xAx fromDistPoint(Point p, double d);
static xAx fromLine(Point n, double d);
static xAx fromLine(Line l);
static xAx fromPoints(std::vector<Point> const &pts);
template<typename T>
T evaluate_at(T x, T y) const {
return c[0]*x*x + c[1]*x*y + c[2]*y*y + c[3]*x + c[4]*y + c[5];
}
double valueAt(Point P) const;
std::vector<double> implicit_form_coefficients() const {
return std::vector<double>(c, c+6);
}
template<typename T>
T evaluate_at(T x, T y, T w) const {
return c[0]*x*x + c[1]*x*y + c[2]*y*y + c[3]*x*w + c[4]*y*w + c[5]*w*w;
}
xAx scale(double sx, double sy) const;
Point gradient(Point p) const;
xAx operator-(xAx const &b) const;
xAx operator+(xAx const &b) const;
xAx operator+(double const &b) const;
xAx operator*(double const &b) const;
std::vector<Point> crossings(Rect r) const;
boost::optional<RatQuad> toCurve(Rect const & bnd) const;
std::vector<double> roots(Point d, Point o) const;
std::vector<double> roots(Line const &l) const;
static Interval quad_ex(double a, double b, double c, Interval ivl);
Geom::Affine hessian() const;
boost::optional<Point> bottom() const;
Interval extrema(Rect r) const;
/*
* Return the symmetric matrix related to the conic section.
* Modifying the matrix does not modify the conic section
*/
NL::SymmetricMatrix<3> get_matrix() const
{
NL::SymmetricMatrix<3> C(c);
C(1,0) *= 0.5; C(2,0) *= 0.5; C(2,1) *= 0.5;
return C;
}
/*
* Return the i-th coefficient of the conic section algebraic equation
* Modifying the returned value does not modify the conic section coefficient
*/
double coeff (size_t i) const
{
return c[i];
}
/*
* Return the i-th coefficient of the conic section algebraic equation
* Modifying the returned value modifies the conic section coefficient
*/
double& coeff (size_t i)
{
return c[i];
}
kind_t kind () const;
std::string categorise() const;
/*
* Return true if the equation:
* c0*x^2 + c1*xy + c2*y^2 + c3*x + c4*y +c5 == 0
* really defines a conic, false otherwise
*/
bool is_quadratic() const
{
return (coeff(0) != 0 || coeff(1) != 0 || coeff(2) != 0);
}
/*
* Return true if the conic is degenerate, i.e. if the related matrix
* determinant is null, false otherwise
*/
bool isDegenerate() const
{
return (det_sgn (get_matrix()) == 0);
}
/*
* Compute the centre of simmetry of the conic section when it exists,
* else it return an unitialized boost::optional<Point> instance.
*/
boost::optional<Point> centre() const
{
typedef boost::optional<Point> opt_point_t;
double d = coeff(1) * coeff(1) - 4 * coeff(0) * coeff(2);
if (are_near (d, 0)) return opt_point_t();
NL::Matrix Q(2, 2);
Q(0,0) = coeff(0);
Q(1,1) = coeff(2);
Q(0,1) = Q(1,0) = coeff(1) * 0.5;
NL::Vector T(2);
T[0] = - coeff(3) * 0.5;
T[1] = - coeff(4) * 0.5;
NL::LinearSystem ls (Q, T);
NL::Vector sol = ls.SV_solve();
Point C;
C[0] = sol[0];
C[1] = sol[1];
return opt_point_t(C);
}
double axis_angle() const;
void roots (std::vector<double>& sol, Coord v, Dim2 d) const;
xAx translate (const Point & _offset) const;
xAx rotate (double angle) const;
/*
* Rotate the conic section by the given angle wrt the provided point.
*
* _rot_centre: the rotation centre
* _angle: the rotation angle
*/
xAx rotate (const Point & _rot_centre, double _angle) const
{
xAx result
= translate (-_rot_centre).rotate (_angle).translate (_rot_centre);
return result;
}
/*
* Compute the tangent line of the conic section at the provided point
*
* _point: the conic section point the tangent line pass through
*/
Line tangent (const Point & _point) const
{
NL::Vector pp(3);
pp[0] = _point[0]; pp[1] = _point[1]; pp[2] = 1;
NL::SymmetricMatrix<3> C = get_matrix();
NL::Vector line = C * pp;
return Line(line[0], line[1], line[2]);
}
/*
* For a non degenerate conic compute the dual conic.
* TODO: investigate degenerate case
*/
xAx dual () const
{
//assert (! isDegenerate());
NL::SymmetricMatrix<3> C = get_matrix();
NL::SymmetricMatrix<3> D = adj(C);
xAx dc(D);
return dc;
}
bool decompose (Line& l1, Line& l2) const;
/*
* Generate a RatQuad object from a conic arc.
*
* p0: the initial point of the arc
* p1: the inner point of the arc
* p2: the final point of the arc
*/
RatQuad toRatQuad (const Point & p0,
const Point & p1,
const Point & p2) const
{
Point dp0 = gradient (p0);
Point dp2 = gradient (p2);
return
RatQuad::fromPointsTangents (p0, rot90 (dp0), p1, p2, rot90 (dp2));
}
/*
* Return the angle related to the normal gradient computed at the passed
* point.
*
* _point: the point at which computes the angle
*
* prerequisite: the passed point must lie on the conic
*/
double angle_at (const Point & _point) const
{
double angle = atan2 (gradient (_point));
if (angle < 0) angle += (2*M_PI);
return angle;
}
/*
* Return true if the given point is contained in the conic arc determined
* by the passed points.
*
* _point: the point to be tested
* _initial: the initial point of the arc
* _inner: an inner point of the arc
* _final: the final point of the arc
*
* prerequisite: the passed points must lie on the conic, the inner point
* has to be strictly contained in the arc, except when the
* initial and final points are equal: in such a case if the
* inner point is also equal to them, then they define an arc
* made up by a single point.
*
*/
bool arc_contains (const Point & _point, const Point & _initial,
const Point & _inner, const Point & _final) const
{
double pa = angle_at (_point);
double sa = angle_at (_initial);
double ia = angle_at (_inner);
double ea = angle_at (_final);
// we test if _point and _inner have the same position
// wrt _initial and _final
return Geom::arc_contains (pa, sa, ia, ea);
}
Rect arc_bound (const Point & P1, const Point & Q, const Point & P2) const;
std::vector<Point> allNearestTimes (const Point &P) const;
/*
* Return the point on the conic section nearest to the passed point "P".
*
* P: the point to compute the nearest one
*/
Point nearestTime (const Point &P) const
{
std::vector<Point> points = allNearestTimes (P);
if ( !points.empty() )
{
return points.front();
}
// else
THROW_LOGICALERROR ("nearestTime: no nearest point found");
return Point();
}
};
std::vector<Point> intersect(const xAx & C1, const xAx & C2);
bool clip (std::vector<RatQuad> & rq, const xAx & cs, const Rect & R);
inline std::ostream &operator<< (std::ostream &out_file, const xAx &x) {
for(int i = 0; i < 6; i++) {
out_file << x.c[i] << ", ";
}
return out_file;
}
};
#endif // LIB2GEOM_SEEN_CONICSEC_H
/*
Local Variables:
mode:c++
c-file-style:"stroustrup"
c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
indent-tabs-mode:nil
fill-column:99
End:
*/
// vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:fileencoding=utf-8:textwidth=99 :