/*

 * FUNCTION:

 * This file contains a number of utilities useful to 3D graphics in

 * general, and to the generation of tubing and extrusions in particular

 * 

 * HISTORY:

 * Written by Linas Vepstas, August 1991

 */

#ifdef __APPLE__

#include "gle_osx.h"

#endif

#include "gutil.h"

#include "intersect.h"

/* ========================================================== */

/* 

 * The macro and subroutine INTERSECT are designed to compute the

 * intersection of a line (defined by the points v1 and v2) and a plane

 * (defined as plane which is normal to the vector n, and contains the

 * point p).  Both sect the array "sect", which is the point of

 * interesection.

 * 

 * The subroutine returns a value indicating if the specified inputs

 * represented a degenerate case. Valid is TRUE if the computed

 * intersection is valid, else it is FALSE.

 */

/* ========================================================== */

void intersect (gleDouble sect[3],  /* returned */

                gleDouble p[3], /* input */

                gleDouble n[3], /* input */

                gleDouble v1[3],    /* input */

                gleDouble v2[3])    /* input */

{

   INTERSECT (sect, p, n, v1, v2);

}

/* ========================================================== */

/* 

 * The macro and subroutine BISECTING_PLANE compute a normal vecotr that

 * describes the bisecting plane between three points (v1, v2 and v3).  

 * This bisecting plane has the following properties:

 * 1) it contains the point v2

 * 2) the angle it makes with v21 == v2 - v1 is equal to the angle it 

 *    makes with v32 == v3 - v2 

 * 3) it is perpendicular to the plane defined by v1, v2, v3.

 *

 * Having input v1, v2, and v3, it returns a vector n.

 * Note that n is NOT normalized (is NOT of unit length).

 * 

 * The subroutine returns a value indicating if the specified inputs

 * represented a degenerate case. Valid is TRUE if the computed

 * intersection is valid, else it is FALSE.

 */

int bisecting_plane (gleDouble n[3],    /* returned */

                      gleDouble v1[3],  /* input */

                      gleDouble v2[3],  /* input */

                      gleDouble v3[3])  /* input */

{

   int valid;

   BISECTING_PLANE (valid, n, v1, v2, v3);

   return (valid);

}

/* ========================================================== */