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Index Page ucrss_c

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Procedure Abstract Required_Reading Keywords Brief_I/O Detailed_Input | Detailed_Output Parameters Exceptions Files Particulars Examples | Restrictions Literature_References Author_and_Institution Version Index_Entries

#### 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

#### Link to routine ucrss_c source file ucrss_c.c

    Fri Dec 31 18:41:14 2021