/* util.c - Don Yang (uguu.org)

   06/07/03
                                                                           */
/*@ -realcompare @*/

#include"global.h"
#include"util.h"


/******************************************************************* Cross */
void Cross(double ax, double ay, double az,
           double bx, double by, double bz,
           /*@out@*/double *ox, /*@out@*/double *oy, /*@out@*/double *oz)
{
   *ox = ay * bz - by * az;
   *oy = az * bx - bz * ax;
   *oz = ax * by - bx * ay;

} /* Cross() */

/*************************************************************** Normalize */
void Normalize(double *x, double *y, double *z, double unit)
{
   double r;

   r = sqrt(*x * *x + *y * *y + *z * *z);
   assert(r > 0.0);
   unit /= r;
   *x *= unit;
   *y *= unit;
   *z *= unit;

} /* Normalize() */

/************************************************************* RotatePoint */
void RotatePoint(double theta, double phi, double *x, double *y, double *z)
{
   double i, j, k;

   i = *x;
   j = *y;
   k = *z;
   *x = cos(theta) * i - sin(theta)*sin(phi) * j - sin(theta)*cos(phi) * k;
   *y =                             cos(phi) * j            - sin(phi) * k;
   *z = sin(theta) * i + cos(theta)*sin(phi) * j + cos(theta)*cos(phi) * k;

} /* RotatePoint() */