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/* distance.c */
/* avr.math.geometry  Geometry math module. {{{
*
* Copyright (C) 2010 Nicolas Schodet
*
* APBTeam:
* Web: http://apbteam.org/
* Email: team AT apbteam DOT org
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place  Suite 330, Boston, MA 021111307, USA.
*
* }}} */
#include "common.h"
#include "distance.h"
#include "modules/utils/utils.h"
int16_t
distance_segment_point (vect_t *a, vect_t *b, vect_t *p)
{
int16_t proj;
/* The space is split in three regions delimited by the two parallel lines
* going through A and B, perpendicular to the segment:
*
*  
*  2 
*  
* 1 A=======B 3
*  
*  2 
*  
*
* If P is in region 2, distance is the distance between P and the AB
* line.
*
* If P is in region 1, distance is AP. If P is in region 3, distance
* is BP.
*
* If vAP . vAB <= 0, P is in region 1. If vBP . vAB > 0, P is in region
* 3. Else, it is in region 2.
*
* Distance to line is determined using dot product between vn, a normal
* of vAB and vBP. */
vect_t vab, vap, vbp;
/* Region 1? */
vab = *b; vect_sub (&vab, a);
vap = *p; vect_sub (&vap, a);
if (vect_dot_product (&vab, &vap) <= 0)
return vect_norm (&vap);
/* Region 3? */
vbp = *p; vect_sub (&vbp, b);
if (vect_dot_product (&vab, &vbp) > 0)
return vect_norm (&vbp);
/* Else, region 2. */
vect_normal (&vab);
proj = vect_dot_product (&vab, &vbp) / vect_norm (&vab);
return UTILS_ABS (proj);
}
