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root |
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/* |
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* graphical interfaces |
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*/ |
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#include "config.h" |
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#include "interface.h" |
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// the simplest way I could imagine fast enough to find out wether a polygon |
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// is clockwise or ccw could probably be *much* faster |
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// |
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double winding (const points &v) t_no |
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{ |
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double wind = 0; |
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points::const_iterator a = v.begin (); |
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points::const_iterator b = a; b++; |
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points::const_iterator c = b; c++; |
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for (;;) |
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{ |
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if (c == v.end ()) c = v.begin (); |
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if (b == v.end ()) b = v.begin (); |
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if (a == v.end ()) return wind; |
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vec d = cross (b->v - a->v, c->v - b->v); |
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if (abs (d) > 1e-6) // ignore almost coincident edges |
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wind += normalize (d) * normalize (b->n); |
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++c; |
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++b; |
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++a; |
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} |
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} |
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