Index Page cgv2el_c

A B C D E F G H I J K L M N O P Q R S T U V W X

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

       void cgv2el_c ( ConstSpiceDouble    center[3],
                       ConstSpiceDouble    vec1  [3],
                       ConstSpiceDouble    vec2  [3],
                       SpiceEllipse      * ellipse   )

#### Abstract

       Form a CSPICE ellipse from a center vector and two generating
       vectors.

#### Required_Reading

       ELLIPSES

#### Keywords

       ELLIPSE
       GEOMETRY

#### Brief_I/O

       Variable  I/O  Description
       --------  ---  --------------------------------------------------
       center,
       vec1,
       vec2       I   Center and two generating vectors for an ellipse.
       ellipse    O   The CSPICE ellipse defined by the input vectors.

#### Detailed_Input

       center,
       vec1,
       vec2           are a center and two generating vectors defining
                      an ellipse in three-dimensional space.  The
                      ellipse is the set of points

                         center  +  cos(theta) vec1  +  sin(theta) vec2

                      where theta ranges over the interval (-pi, pi].
                      vec1 and vec2 need not be linearly independent.

#### Detailed_Output

       ellipse        is the CSPICE ellipse defined by the input
                      vectors.

#### Parameters

       None.

#### Exceptions

       1)  If vec1 and vec2 are linearly dependent, ellips will be
           degenerate.  CSPICE ellipses are allowed to represent
           degenerate geometric ellipses.

#### Files

       None.

#### Particulars

       CSPICE ellipses serve to simplify calling sequences and reduce
       the chance for error in declaring and describing argument lists
       involving ellipses.

       The set of ellipse conversion routines is

          cgv2el_c ( Center and generating vectors to ellipse )
          el2cgv_c ( Ellipse to center and generating vectors )

#### Examples

       1)  Find the intersecton of an ellipse with a plane.  The ellipse
           is defined by the vectors center, vec1, and vec2.  The plane
           is defined by the normal vector n and the constant c.

              #include "SpiceUsr.h"
                        .
                        .
                        .
              /.
              Make a CSPICE ellipse.  Make a plane while we're at it.
              ./
              cgv2el_c ( center, vec1, vec2,  &ellipse );
              nvc2pl_c ( n,      c,           &plane   );

              /.
              Find the intersection of the ellipse and plane.
              nxpts is the number of intersection points; xpt1
              and xpt2 are the points themselves.
              ./
              inelpl_c ( &ellipse, &plane, &nxpts, xpt1, xpt2 );

#### Restrictions

       None.

#### Literature_References

       None.

#### Author_and_Institution

       N.J. Bachman   (JPL)

#### Version

       -CSPICE Version 1.0.0, 05-MAR-1999 (NJB)

#### Index_Entries

       center and generating vectors to ellipse

#### Link to routine cgv2el_c source file cgv2el_c.c

    Wed Apr  5 17:54:29 2017