flightgear/Math/vector.cxx

/**************************************************************************
 * vector.c -- additional vector routines
 *
 * Written by Curtis Olson, started December 1997.
 *
 * Copyright (C) 1997  Curtis L. Olson  - curt@infoplane.com
 *
 * 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., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 * $Id$
 * (Log is kept at end of this file)
 **************************************************************************/


#include <math.h>
#include <stdio.h>

#include <Include/fg_types.h>

#include "vector.hxx"

#include "mat3.h"


#if !defined( USE_XTRA_MAT3_INLINES )
/* Map a vector onto the plane specified by normal */
void map_vec_onto_cur_surface_plane(MAT3vec normal, MAT3vec v0, MAT3vec vec,
				    MAT3vec result)
{
    MAT3vec u1, v, tmp;

    /* calculate a vector "u1" representing the shortest distance from
     * the plane specified by normal and v0 to a point specified by
     * "vec".  "u1" represents both the direction and magnitude of
     * this desired distance. */

    /* u1 = ( (normal <dot> vec) / (normal <dot> normal) ) * normal */

    MAT3_SCALE_VEC( u1,
		    normal,
		    ( MAT3_DOT_PRODUCT(normal, vec) /
		      MAT3_DOT_PRODUCT(normal, normal)
		      )
		    );

    /*
    printf("  vec = %.2f, %.2f, %.2f\n", vec[0], vec[1], vec[2]);
    printf("  v0 = %.2f, %.2f, %.2f\n", v0[0], v0[1], v0[2]);
    printf("  u1 = %.2f, %.2f, %.2f\n", u1[0], u1[1], u1[2]);
    */

    /* calculate the vector "v" which is the vector "vec" mapped onto
       the plane specified by "normal" and "v0". */

    /* v = v0 + vec - u1 */

    MAT3_ADD_VEC(tmp, v0, vec);
    MAT3_SUB_VEC(v, tmp, u1);
    /* printf("  v = %.2f, %.2f, %.2f\n", v[0], v[1], v[2]); */

    /* Calculate the vector "result" which is "v" - "v0" which is a
     * directional vector pointing from v0 towards v */

    /* result = v - v0 */

    MAT3_SUB_VEC(result, v, v0);
    /* printf("  result = %.2f, %.2f, %.2f\n", 
       result[0], result[1], result[2]); */
}
#endif // !defined( USE_XTRA_MAT3_INLINES )


// Given a point p, and a line through p0 with direction vector d,
// find the shortest distance from the point to the line
double fgPointLine(MAT3vec p, MAT3vec p0, MAT3vec d) {
    MAT3vec u, u1, v;
    double ud, dd, tmp, dist;
    
    // u = p - p0
    MAT3_SUB_VEC(u, p, p0);

    // calculate the projection, u1, of u along d.
    // u1 = ( dot_prod(u, d) / dot_prod(d, d) ) * d;
    ud = MAT3_DOT_PRODUCT(u, d);
    dd = MAT3_DOT_PRODUCT(d, d);
    tmp = ud / dd;

    MAT3_SCALE_VEC(u1, d, tmp);;

    // v = u - u1 = vector from closest point on line, p1, to the
    // original point, p.
    MAT3_SUB_VEC(v, u, u1);

    dist = sqrt(MAT3_DOT_PRODUCT(v, v));

    return( dist );
}


// Given a point p, and a line through p0 with direction vector d,
// find the shortest distance (squared) from the point to the line
double fgPointLineSquared(MAT3vec p, MAT3vec p0, MAT3vec d) {
    MAT3vec u, u1, v;
    double ud, dd, tmp;
    
    // u = p - p0
    MAT3_SUB_VEC(u, p, p0);

    // calculate the projection, u1, of u along d.
    // u1 = ( dot_prod(u, d) / dot_prod(d, d) ) * d;
    ud = MAT3_DOT_PRODUCT(u, d);
    dd = MAT3_DOT_PRODUCT(d, d);
    tmp = ud / dd;

    MAT3_SCALE_VEC(u1, d, tmp);;

    // v = u - u1 = vector from closest point on line, p1, to the
    // original point, p.
    MAT3_SUB_VEC(v, u, u1);

    return ( MAT3_DOT_PRODUCT(v, v) );
}


/* $Log$
/* Revision 1.3  1998/08/24 20:04:12  curt
/* Various "inline" code optimizations contributed by Norman Vine.
/*
 * Revision 1.2  1998/07/24 21:34:38  curt
 * fgPointLine() rewritten into fgPointLineSquared() ... this ultimately saves
 * us from doing a sqrt().
 *
 * Revision 1.1  1998/07/08 14:40:10  curt
 * polar3d.[ch] renamed to polar3d.[ch]xx, vector.[ch] renamed to vector.[ch]xx
 * Updated fg_geodesy comments to reflect that routines expect and produce
 *   meters.
 *
 * Revision 1.3  1998/05/07 23:04:28  curt
 * Added a blank formating line!
 *
 * Revision 1.2  1998/01/19 19:27:13  curt
 * Merged in make system changes from Bob Kuehne <rpk@sgi.com>
 * This should simplify things tremendously.
 *
 * Revision 1.1  1997/12/22 04:13:17  curt
 * Initial revision.
 * */