cgv2el_c

 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,
ConstSpiceDouble    vec1  ,
ConstSpiceDouble    vec2  ,
SpiceEllipse      * ellipse   )

```

#### Abstract

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

```
ELLIPSES
```

```
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.
```

```
None.
```

#### Exceptions

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

```
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 );

```

```
None.
```

```
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
```
`Wed Apr  5 17:54:29 2017`