Root/
| 1 | /* |
| 2 | * v2d_line_distance.c - Calculate the distance between a point and a line |
| 3 | * |
| 4 | * Written 2012 by Werner Almesberger |
| 5 | * Copyright 2012 Werner Almesberger |
| 6 | * |
| 7 | * This library is free software; you can redistribute it and/or |
| 8 | * modify it under the terms of the GNU Lesser General Public |
| 9 | * License as published by the Free Software Foundation; either |
| 10 | * version 2.1 of the License, or (at your option) any later version. |
| 11 | */ |
| 12 | |
| 13 | |
| 14 | #include <math.h> |
| 15 | |
| 16 | #include "poly2d.h" |
| 17 | |
| 18 | |
| 19 | /* |
| 20 | * We use formula (14) from |
| 21 | * http://mathworld.wolfram.com/Point-LineDistance2-Dimensional.html |
| 22 | * but keep the sign. |
| 23 | */ |
| 24 | |
| 25 | double v2d_line_distance(const struct v2d *a, const struct v2d *b, |
| 26 | const struct v2d *p) |
| 27 | { |
| 28 | double ax, ay; |
| 29 | |
| 30 | ax = b->x-a->x; |
| 31 | ay = b->y-a->y; |
| 32 | |
| 33 | return (ax*(a->y-p->y)-ay*(a->x-p->x))/hypot(ax, ay); |
| 34 | } |
| 35 |
Branches:
master
