Procedure

   void vperp_c ( ConstSpiceDouble   a[3],
                  ConstSpiceDouble   b[3],
                  SpiceDouble        p[3] )

Abstract

   Find the component of a vector that is perpendicular to a second
   vector.  All vectors are 3-dimensional.

Required_Reading

   None.

Keywords

   VECTOR

Brief_I/O

   VARIABLE  I/O  DESCRIPTION
   --------  ---  --------------------------------------------------
    a         I    The vector whose orthogonal component is sought.
    b         I    The vector used as the orthogonal reference.
    p         O    The component of a orthogonal to b.

Detailed_Input

   a     is a double precision, 3-dimensional vector.  It the vector
         whose component orthogonal to b is sought. (There is a
         unique decomposition of a into a sum v + p, where v is
         parallel to b and p is orthogonal to b.  We want the
         component p.)

   b     is a double precision, 3-dimensional vector.  This
         vector is the vector used as a reference for the
         decomposition of a.

Detailed_Output

   p     is a double precision, 3-dimensional vector containing
         the component of a that is orthogonal to b.
         p may overwrite either a or b.

Parameters

   None.

Exceptions

   Error free.

Files

   None.

Particulars

   Given and non-zero vector b and a vector a, there is a unique
   decomposition of a as a sum v + p such that p is orthogonal
   to b and v is parallel to b.  This routine finds the vector p.

   If b is a zero vector, p will be identical to a.

Examples

   The following table gives sample inputs and results from calling
   vperp_c.

   a                  b                 p
   ------------------------------------------
   (6, 6, 6)      ( 2, 0, 0)        (0, 6, 6)
   (6, 6, 6)      (-3, 0, 0)        (0, 6, 6)
   (6, 6, 0)      ( 0, 7, 0)        (6, 0, 0)
   (6, 0, 0)      ( 0, 0, 9)        (6, 0, 0)

Restrictions

   None.

Literature_References

   REFERENCE: Any reasonable calculus text (for example Thomas)

Author_and_Institution

   W.L. Taber      (JPL)

Version

   -CSPICE Version 1.2.1, 24-APR-2010 (EDW)

      Minor edit to code comments eliminating typo.

   -CSPICE Version 1.2.0, 22-OCT-1998 (NJB)

      Made input vectors const.

   -CSPICE Version 1.1.0, 06-MAR-1998   (EDW)

      Removed non printing character.

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

Index_Entries

   perpendicular component of a 3-vector

Link to routine vperp_c source file vperp_c.c