Procedure

   ucrss_c ( Unitized cross product, 3x3 ) 

   void ucrss_c ( ConstSpiceDouble   v1[3],
                  ConstSpiceDouble   v2[3],
                  SpiceDouble        vout[3] )

Abstract

   Compute the normalized cross product of two 3-vectors.

Required_Reading

   None.

Keywords

   VECTOR

Brief_I/O

   VARIABLE  I/O  DESCRIPTION
   --------  ---  --------------------------------------------------
   v1         I   Left vector for cross product.
   v2         I   Right vector for cross product.
   vout       O   Normalized cross product of `v1' and `v2'.

Detailed_Input

   v1,
   v2          are two double precision 3-dimensional vectors.
               Typically, these might represent the (possibly unit)
               vector to a planet, Sun, or a star which defines the
               orientation of axes of some reference frame.

Detailed_Output

   vout        is the double precision 3-dimensional normalized cross
               product of `v1' and `v2'. `vout' is the result of the
               computation

                      v1 x v2
                  -----------
                   || v1 x v2 ||

               where "x" denotes the cross product and ||x||| the norm
               of a vector `x'.

Parameters

   None.

Exceptions

   Error free.

   1)  If the cross product of `v1' and `v2' yields the zero-vector,
       then the zero-vector is returned instead of a vector of
       unit length.

Files

   None.

Particulars

   None.

Examples

   The numerical results shown for this example may differ across
   platforms. The results depend on the SPICE kernels used as
   input, the compiler and supporting libraries, and the machine
   specific arithmetic implementation.

   1) Define two sets of vectors and compute the normalized cross
      product of each vector in first set and the corresponding
      vector in the second set.


      Example code begins here.


      /.
         Program ucrss_ex1
      ./
      #include <stdio.h>
      #include "SpiceUsr.h"

      int main( )
      {

         /.
         Local parameters.
         ./
         #define NDIM         3
         #define SETSIZ       2

         /.
         Local variables.
         ./
         SpiceDouble          vout   [NDIM];

         SpiceInt             i;

         /.
         Define the two vector sets.
         ./
         SpiceDouble          v1     [SETSIZ][NDIM] = {
                                   { 0.0,  1.0,  0.0 },
                                   { 5.0,  5.0,  5.0 } };

         SpiceDouble          v2     [SETSIZ][NDIM] = {
                                   { 3.0,  0.0,  0.0 },
                                   {-2.0, -2.0, -2.0 } };

         /.
         Calculate the cross product of each pair of vectors
         ./
         for ( i = 0; i < SETSIZ; i++ )
         {
            ucrss_c ( v1[i], v2[i], vout );

            printf( "Vector A                :  %4.1f %4.1f %4.1f\n",
                                         v1[i][0], v1[i][1], v1[i][2] );
            printf( "Vector B                :  %4.1f %4.1f %4.1f\n",
                                         v2[i][0], v2[i][1], v2[i][2] );
            printf( "Normalized cross product:  %4.1f %4.1f %4.1f\n",
                                            vout[0], vout[1], vout[2] );
            printf( "\n" );
         }

         return ( 0 );
      }


      When this program was executed on a Mac/Intel/cc/64-bit
      platform, the output was:


      Vector A                :   0.0  1.0  0.0
      Vector B                :   3.0  0.0  0.0
      Normalized cross product:   0.0  0.0 -1.0

      Vector A                :   5.0  5.0  5.0
      Vector B                :  -2.0 -2.0 -2.0
      Normalized cross product:   0.0  0.0  0.0

Restrictions

   None.

Literature_References

   None.

Author_and_Institution

   N.J. Bachman        (JPL)
   J. Diaz del Rio     (ODC Space)
   W.M. Owen           (JPL)
   W.L. Taber          (JPL)
   E.D. Wright         (JPL)

Version

   -CSPICE Version 1.1.1, 22-MAY-2020 (JDR)

       Edited the header to comply with NAIF standard. Added complete
       code example.

   -CSPICE Version 1.1.0, 22-OCT-1998 (NJB)

       Made input vectors const.

   -CSPICE Version 1.0.0, 08-FEB-1998 (EDW) (WMO) (WLT)

Index_Entries

   unitized cross product