2 spring.cc -- declare Spring
4 source file of the GNU LilyPond music typesetter
6 (c) 2007 Joe Neeman <joeneeman@gmail.com>
15 inverse_stretch_strength_
= 1.0;
16 inverse_compress_strength_
= 1.0;
18 update_blocking_force ();
21 Spring::Spring (Real dist
, Real min_dist
)
27 set_min_distance (min_dist
);
28 set_default_strength ();
29 update_blocking_force ();
33 Spring::update_blocking_force ()
35 if (distance_
== min_distance_
)
36 blocking_force_
= 0.0;
38 blocking_force_
= (min_distance_
- distance_
) / inverse_compress_strength_
;
41 /* scale a spring, but in a way that doesn't violate min_distance */
43 Spring::operator*= (Real r
)
45 distance_
= max (min_distance_
, distance_
* r
);
46 inverse_compress_strength_
= distance_
- min_distance_
;
47 inverse_stretch_strength_
*= 0.8;
51 Spring::operator> (Spring
const &other
) const
53 return blocking_force_
> other
.blocking_force_
;
56 /* merge springs, basically by averaging them, but leave a little headroom
57 above the largest minimum distance so that things don't get too cramped */
59 merge_springs (vector
<Spring
> const &springs
)
61 Real avg_distance
= 0;
62 Real min_distance
= 0;
64 Real avg_compress
= 0;
66 for (vsize i
= 0; i
< springs
.size (); i
++)
68 avg_distance
+= springs
[i
].distance ();
69 avg_stretch
+= springs
[i
].inverse_stretch_strength ();
70 avg_compress
+= 1 / springs
[i
].inverse_compress_strength ();
71 min_distance
= max (springs
[i
].min_distance (), min_distance
);
74 avg_stretch
/= springs
.size ();
75 avg_compress
/= springs
.size ();
76 avg_distance
/= springs
.size ();
77 avg_distance
= max (min_distance
+ 0.3, avg_distance
);
79 Spring ret
= Spring (avg_distance
, min_distance
);
80 ret
.set_inverse_stretch_strength (avg_stretch
);
81 ret
.set_inverse_compress_strength (1 / avg_compress
);
87 Spring::set_distance (Real d
)
89 if (d
< 0 || isinf (d
) || isnan (d
))
90 programming_error ("insane spring distance requested, ignoring it");
93 min_distance_
= min (min_distance_
, d
);
95 update_blocking_force ();
100 Spring::set_min_distance (Real d
)
102 if (d
< 0 || isinf (d
) || isnan (d
))
103 programming_error ("insane spring min_distance requested, ignoring it");
107 distance_
= max (distance_
, min_distance_
);
108 update_blocking_force ();
113 Spring::set_inverse_stretch_strength (Real f
)
115 if (isinf (f
) || isnan (f
) || f
< 0)
116 programming_error ("insane spring constant");
118 inverse_stretch_strength_
= f
;
122 Spring::set_inverse_compress_strength (Real f
)
124 if (isinf (f
) || isnan (f
) || f
< 0)
125 programming_error ("insane spring constant");
127 inverse_compress_strength_
= f
;
129 update_blocking_force ();
133 Spring::set_blocking_force (Real f
)
135 if (isinf (f
) || isnan (f
))
137 programming_error ("insane blocking force");
141 blocking_force_
= -infinity_f
;
142 min_distance_
= length (f
);
143 distance_
= max (distance_
, min_distance_
);
144 update_blocking_force ();
148 Spring::set_default_strength ()
150 inverse_compress_strength_
= distance_
- min_distance_
;
151 inverse_stretch_strength_
= distance_
- min_distance_
;
155 Spring::length (Real f
) const
157 Real force
= max (f
, blocking_force_
);
158 Real inv_k
= force
< 0.0 ? inverse_compress_strength_
: inverse_stretch_strength_
;
162 programming_error ("cruelty to springs");
166 return distance_
+ force
* inv_k
;