vector/vedit/distance.c

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/*!
   \file lib/vector/vedit/distance.c
 
   \brief Vedit library - distance calculation
 
   (C) 2007-2008 by the GRASS Development Team
 
   This program is free software under the GNU General Public License
   (>=v2).  Read the file COPYING that comes with GRASS for details.
 
   \author Martin Landa <landa.martin gmail.com>
 */
 
#include <grass/vedit.h>
 
/*!
   \brief Calculate distances between two lines
 
   \todo LL projection
 
   \param Points1 first line geometry
   \param Points2 second line geometry
   \param with_z WITH_Z for 3D data
   \param[out] mindistidx index of minimal distance
 
   \return minimal distance between two lines (their nodes)
 */
double Vedit_get_min_distance(struct line_pnts *Points1,
                              struct line_pnts *Points2, int with_z,
                              int *mindistidx)
{
    unsigned int i;
    double distances[4];
 
    /*
       distances[0] = first-first
       distances[1] = first-last
       distances[2] = last-first
       distances[3] = last-last
     */
 
    distances[0] = Vect_points_distance(Points1->x[0], Points1->y[0],
                                        Points1->z[0], Points2->x[0],
                                        Points2->y[0], Points2->z[0], with_z);
 
    distances[1] = Vect_points_distance(
        Points1->x[0], Points1->y[0], Points1->z[0],
        Points2->x[Points2->n_points - 1], Points2->y[Points2->n_points - 1],
        Points2->z[Points2->n_points - 1], with_z);
 
    distances[2] = Vect_points_distance(
        Points1->x[Points1->n_points - 1], Points1->y[Points1->n_points - 1],
        Points1->z[Points1->n_points - 1], Points2->x[0], Points2->y[0],
        Points2->z[0], with_z);
 
    distances[3] = Vect_points_distance(
        Points1->x[Points1->n_points - 1], Points1->y[Points1->n_points - 1],
        Points1->z[Points1->n_points - 1], Points2->x[Points2->n_points - 1],
        Points2->y[Points2->n_points - 1], Points2->z[Points2->n_points - 1],
        with_z);
 
    /* find the minimal distance between first or last point of both lines */
    *mindistidx = 0;
    for (i = 0; i < sizeof(distances) / sizeof(double); i++) {
        if (distances[i] >= 0.0 && distances[i] < distances[*mindistidx])
            *mindistidx = i;
    }
 
    G_debug(3, "Vedit_get_min_distance(): dists=%f,%f,%f,%f", distances[0],
            distances[1], distances[2], distances[3]);
 
    return distances[*mindistidx];
}