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35 lines
788 B
C
35 lines
788 B
C
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/*
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* v2d_line_distance.c - Calculate the distance between a point and a line
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*
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* Written 2012 by Werner Almesberger
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* Copyright 2012 Werner Almesberger
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*/
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#include <math.h>
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#include "poly2d.h"
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/*
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* We use formula (14) from
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* http://mathworld.wolfram.com/Point-LineDistance2-Dimensional.html
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* but keep the sign.
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*/
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double v2d_line_distance(const struct v2d *a, const struct v2d *b,
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const struct v2d *p)
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{
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double ax, ay;
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ax = b->x-a->x;
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ay = b->y-a->y;
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return (ax*(a->y-p->y)-ay*(a->x-p->x))/hypot(ax, ay);
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}
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