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Abstract
I/O
Examples
Particulars
Required Reading
Version
Index_Entries

Abstract


   CSPICE_PJELPL orthogonally projects an ellipse onto a plane.

   For important details concerning this module's function, please refer to
   the CSPICE routine pjelpl_c.

I/O


   Given:

      elin    a SPICE ellipse structure. The structure has the fields:

                 center:    [3-array double]
                 semiMajor: [3-array double]
                 semiMinor: [3-array double]

      plane   a SPICE plane structure. The structure has the fields:

                 normal:   [3-array double]
                 constant: [scalar double]

              are, respectively, a SPICE ellipse and a SPICE plane. The
              geometric ellipse represented by 'elin' is to be orthogonally
              projected onto the geometric plane represented by 'plane'.

   the call:

      cspice_pjelpl, elin, plane, elout

   returns:

      elout    the SPICE ellipse structure that represents the geometric
               ellipse resulting from orthogonally projecting the ellipse
               represented by 'elin' onto the plane represented by 'plane'.
               The structure has the fields:

                 center:    [3-array double]
                 semiMajor: [3-array double]
                 semiMinor: [3-array double]

Examples


   Any numerical results shown for this example may differ between
   platforms as the results depend on the SPICE kernels used as input
   and the machine specific arithmetic implementation.

      ;;
      ;; Assign the values for plane/ellipse definition
      ;; vectors.
      ;;
      center  = [ 1.d,  1.d,  1.d ]
      vect1   = [ 2.d,  0.d,  0.d ]
      vect2   = [ 0.d,  1.d,  1.d ]
      normal  = [ 0.d,  0.d,  1.d ]

      ;;
      ;; Create a plane using a constant value of 0...
      ;;
      cspice_nvc2pl, normal, 0.d, plane

      ;;
      ;; ...and an ellipse.
      ;;
      cspice_cgv2el, center, vect1, vect2, elin

      ;;
      ;; Project the ellipse onto the plane.
      ;;
      cspice_pjelpl, elin, plane, elout

      ;;
      ;; Output the ellipse in the plane.
      ;;
      print, 'Center    : ', elout.center
      print, 'Semi-minor: ', elout.semiminor
      print, 'Semi-major: ', elout.semimajor

   IDL outputs for the components of 'elout':

      Center    :  1.0000000   1.0000000   0.0000000
      Semi-minor:  0.0000000   1.0000000   0.0000000
      Semi-major:  2.0000000   0.0000000   0.0000000

Particulars


   Projecting an ellipse orthogonally onto a plane can be thought of
   finding the points on the plane that are `under' or `over' the
   ellipse, with the `up' direction considered to be perpendicular
   to the plane.  More mathematically, the orthogonal projection is
   the set of points Y in the plane such that for some point X in
   the ellipse, the vector Y - X is perpendicular to the plane.
   The orthogonal projection of an ellipse onto a plane yields
   another ellipse.

Required Reading


   ICY.REQ
   ELLIPSES.REQ
   PLANES.REQ

Version


   -Icy Version 1.0.1, 13-JUN-2011, EDW (JPL)

      Edits to comply with NAIF standard for Icy headers. Particulars section
      now parallels Mice version.

   -Icy Version 1.0.0, 16-JUN-2003, EDW (JPL)

Index_Entries


   project ellipse onto plane




Wed Apr  5 17:58:02 2017