2 bezier.cc -- implement Bezier and Bezier_bow
4 source file of the GNU LilyPond music typesetter
6 (c) 1998--2000 Jan Nieuwenhuizen <janneke@gnu.org>
13 IS_INF tests its floating point number for infiniteness
14 Ripped from guile's number.c. Solaris has no isinf ().
17 #define isinf(x) ((x) == (x) / 2)
21 #include "polynomial.hh"
24 binomial_coefficient (Real over , int under)
30 x *= over / Real (under);
39 flip (Array<Offset>* arr_p, Axis a)
42 // for (int i = c.size (); i--;)
43 for (int i = 0; i < arr_p->size (); i++)
44 (*arr_p)[i][a] = - (*arr_p)[i][a];
48 rotate (Array<Offset>* arr_p, Real phi)
50 Offset rot (complex_exp (Offset (0, phi)));
51 for (int i = 0; i < arr_p->size (); i++)
52 (*arr_p)[i] = complex_multiply (rot, (*arr_p)[i]);
56 translate (Array<Offset>* arr_p, Offset o)
58 for (int i = 0; i < arr_p->size (); i++)
64 Formula of the bezier 3-spline
66 sum_{j=0}^3 (3 over j) z_j (1-t)^(3-j) t^j
70 Bezier::get_other_coordinate (Axis a, Real x) const
72 Axis other = Axis ((a +1)%NO_AXES);
73 Array<Real> ts = solve_point (a, x);
75 Offset c = curve_point (ts[0]);
76 assert (fabs (c[a] - x) < 1e-8);
83 Bezier::curve_point (Real t)const
86 Real one_min_tj = (1-t)*(1-t)*(1-t);
89 for (int j=0 ; j < 4; j++)
91 o += control_[j] * binomial_coefficient (3, j)
92 * pow (t,j) * pow (1-t, 3-j);
99 assert (fabs (o[X_AXIS] - polynomial (X_AXIS).eval (t))< 1e-8);
100 assert (fabs (o[Y_AXIS] - polynomial (Y_AXIS).eval (t))< 1e-8);
108 Bezier::polynomial (Axis a)const
111 for (int j=0; j <= 3; j++)
114 * Polynomial::power (j , Polynomial (0,1))*
115 Polynomial::power (3 - j, Polynomial (1,-1))*
116 binomial_coefficient(3, j);
123 Remove all numbers outside [0,1] from SOL
126 filter_solutions (Array<Real> sol)
128 for (int i = sol.size (); i--;)
129 if (sol[i] < 0 || sol[i] >1)
135 find t such that derivative is proportional to DERIV
138 Bezier::solve_derivative (Offset deriv)const
140 Polynomial xp=polynomial (X_AXIS);
141 Polynomial yp=polynomial (Y_AXIS);
145 Polynomial combine = xp * deriv[Y_AXIS] - yp * deriv [X_AXIS];
147 return filter_solutions (combine.solve ());
152 Find t such that curve_point (t)[AX] == COORDINATE
155 Bezier::solve_point (Axis ax, Real coordinate) const
157 Polynomial p(polynomial (ax));
158 p.coefs_[0] -= coordinate;
160 Array<Real> sol (p.solve ());
161 return filter_solutions (sol);
165 Bezier::extent (Axis a)const
167 int o = (a+1)%NO_AXES;
171 Array<Real> sols (solve_derivative (d));
174 for (int i= sols.size (); i--;)
176 Offset o (curve_point (sols[i]));
177 iv.unite (Interval (o[a],o[a]));
183 Bezier::flip (Axis a)
185 for (int i = CONTROL_COUNT; i--;)
186 control_[i][a] = - control_[i][a];
190 Bezier::rotate (Real phi)
192 Offset rot (complex_exp (Offset (0, phi)));
193 for (int i = 0; i < CONTROL_COUNT; i++)
194 control_[i] = complex_multiply (rot, control_[i]);
198 Bezier::translate (Offset o)
200 for (int i = 0; i < CONTROL_COUNT; i++)
205 Bezier::assert_sanity () const
207 for (int i=0; i < CONTROL_COUNT; i++)
208 assert (!isnan (control_[i].length ())
209 && !isinf (control_[i].length ()));
216 for (int i =0; i < CONTROL_COUNT; i++)
217 b2.control_[CONTROL_COUNT-i-1] = control_[i];