- Abstract
Form a CSPICE ellipse from a center vector and two generating
vectors.
- Required_Reading
ELLIPSES
- 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.
- 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.
- Exceptions
1) If vec1 and vec2 are linearly dependent, ellips will be
degenerate. CSPICE ellipses are allowed to represent
degenerate geometric ellipses.
- Files
None.
- Author_and_Institution
N.J. Bachman (JPL)
- Literature_References
None.
- Version
-CSPICE Version 1.0.0, 05-MAR-1999 (NJB)
- Index_Entries
center and generating vectors to ellipse
- Link to routine source