/* 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 02111-1307, USA. * * }}} */ #include "common.h" #include "distance.h" #include "modules/utils/utils.h" #include "modules/math/fixed/fixed.h" int16_t distance_point_point (const vect_t *a, const vect_t *b) { int32_t dx = b->x - a->x; int32_t dy = b->y - a->y; return fixed_sqrt_ui32 (dx * dx + dy * dy); } int16_t distance_segment_point (const vect_t *a, const vect_t *b, const 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. */ proj = vect_normal_dot_product (&vab, &vbp) / vect_norm (&vab); return UTILS_ABS (proj); }