void cgv2el_c ( ConstSpiceDouble center,
ConstSpiceDouble vec1 ,
ConstSpiceDouble vec2 ,
SpiceEllipse * ellipse )
Form a CSPICE ellipse from a center vector and two generating
Variable I/O Description
-------- --- --------------------------------------------------
vec2 I Center and two generating vectors for an ellipse.
ellipse O The CSPICE ellipse defined by the input vectors.
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.
ellipse is the CSPICE ellipse defined by the input
1) If vec1 and vec2 are linearly dependent, ellips will be
degenerate. CSPICE ellipses are allowed to represent
degenerate geometric ellipses.
CSPICE ellipses serve to simplify calling sequences and reduce
the chance for error in declaring and describing argument lists
The set of ellipse conversion routines is
cgv2el_c ( Center and generating vectors to ellipse )
el2cgv_c ( Ellipse to center and generating vectors )
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.
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 );
N.J. Bachman (JPL)
-CSPICE Version 1.0.0, 05-MAR-1999 (NJB)
center and generating vectors to ellipse