Procedure

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

Abstract

   Compute the cross product of two 3-dimensional vectors.

Required_Reading

   None.

Keywords

   VECTOR

Brief_I/O

   VARIABLE  I/O  DESCRIPTION
   --------  ---  --------------------------------------------------
   v1         I     Left hand vector for cross product.
   v2         I     Right hand vector for cross product.
   vout       O     Cross product v1xv2.
                    vout can overwrite either v1 or v2.

Detailed_Input

   v1      This may be any 3-dimensional vector.  Typically, this
           might represent the (possibly unit) vector to a planet,
           sun, or a star which defines the orientation of axes of
           some coordinate system.

   v2      Ditto.

Detailed_Output

   vout    This variable represents the cross product of v1 and v2.
           vout may overwrite v1 or v2.

Parameters

   None.

Exceptions

   Error free.

Files

   None.

Particulars

   vcrss_c calculates the three dimensional cross product of two
   vectors according to the definition.  The cross product is stored
   in a buffer vector until the calculation is complete.  Thus vout
   may overwrite v1 or v2 without interfering with intermediate
   computations.

   If v1 and v2 are large in magnitude (taken together, their
   magnitude surpasses the limit allow by the computer) then it may
   be possible to generate a floating point overflow from an
   intermediate computation even though the actual cross product
   may be well within the range of double precision numbers.
   vcrss_c does NOT check the magnitude of v1 or v2 to insure that
   overflow will not occur.

Examples

   v1                  v2                  vout (=v1Xv2)
   -----------------------------------------------------------------
   (0, 1, 0)           (1, 0, 0)           (0, 0, -1)
   (5, 5, 5)           (-1, -1, -1)        (0, 0, 0)

Restrictions

   No checking of v1 or v2 is done to prevent floating point
   overflow. The user is required to determine that the magnitude
   of each component of the vectors is within an appropriate range
   so as not to cause floating point overflow. In almost every case
   there will be no problem and no checking actually needs to be
   done.

Literature_References

   None.

Author_and_Institution

   W.M. Owen       (JPL)
   E.D. Wright     (JPL)

Version

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

      Made input vectors const.

   -CSPICE Version 1.0.1, 06-MAR-1998 (EDW)
   
      Minor header correction.  Added use of MOVED.

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

Index_Entries

   vector cross product

Link to routine vcrss_c source file vcrss_c.c