cspice_vprjp

 Abstract I/O Examples Particulars Required Reading Version Index_Entries
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```

#### Abstract

```
CSPICE_VPRJP orthogonally projects a vector onto a specified plane.

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

```

#### I/O

```
Given:

vin     a double precision 3-vector to orthogonally project onto a
specified plane.

plane   a SPICE plane structure that represents the geometric plane
onto which to project 'vin'. The structure has the ields:

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

the call:

cspice_vprjp, vin, plane, vout

returns:

vout   a double precision 3-vector resulting from the orthogonal
projection of 'vin' onto 'plane'. 'vout' is the closest point
in the specified plane to 'vin'.

```

#### 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.

;;
;; Find the closest point in the ring plane of a planet to a
;; spacecraft located at vec1 (in body-fixed coordinates).
;;
vec1 = [ -5.d, 7.d, 2.2d]

;;
;; Define the vector normal as the normal to the
;; equatorial ring plane, and the origin at body/ring center
;;
norm = [ 0.d, 0.d, 1.d ]
orig = [ 0.d, 0.d, 0.d ]

;;
;; Create the plane structure.
;;
cspice_nvp2pl, norm, orig, ring_plane

;;
;; Project the position vector onto the ring plane...
;;
cspice_vprjp, vec1, ring_plane, proj

IDL returns proj as:    -5.0000000    7.0000000    0.0000000

```

#### Particulars

```
Projecting a vector v orthogonally onto a plane can be thought of
as finding the closest vector in the plane to v.  This `closest
vector' always exists; it may be coincident with the original
vector.

Two related routines are cspice_vprjpi, which inverts an orthogonal
projection of a vector onto a plane, and cspice_vproj, which projects
a vector orthogonally onto another vector.

```

```
ICY.REQ
PLANES.REQ

```

#### Version

```
-Icy Version 1.0.1, 23-NOV-2010, EDW (JPL)

Improved the Particulars and I/O sections. The section now meets NAIF
standard for Icy headers.

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

```

#### Index_Entries

```
vector projection onto plane

```
`Wed Apr  5 17:58:04 2017`