1 |
/* |
2 |
* graphical interfaces |
3 |
*/ |
4 |
|
5 |
#include "config.h" |
6 |
|
7 |
#include "interface.h" |
8 |
|
9 |
// the simplest way I could imagine fast enough to find out wether a polygon |
10 |
// is clockwise or ccw could probably be *much* faster |
11 |
// |
12 |
double winding (const points &v) t_no |
13 |
{ |
14 |
double wind = 0; |
15 |
|
16 |
points::const_iterator a = v.begin (); |
17 |
points::const_iterator b = a; b++; |
18 |
points::const_iterator c = b; c++; |
19 |
|
20 |
for (;;) |
21 |
{ |
22 |
if (c == v.end ()) c = v.begin (); |
23 |
if (b == v.end ()) b = v.begin (); |
24 |
if (a == v.end ()) return wind; |
25 |
|
26 |
vec d = cross (b->v - a->v, c->v - b->v); |
27 |
|
28 |
if (abs (d) > 1e-6) // ignore almost coincident edges |
29 |
wind += normalize (d) * normalize (b->n); |
30 |
|
31 |
++c; |
32 |
++b; |
33 |
++a; |
34 |
} |
35 |
} |
36 |
|
37 |
|