cspice_pltnrm

 Abstract I/O Examples Particulars Required Reading Version Index_Entries

#### Abstract

```
CSPICE_PLTNRM computes an outward normal vector of a triangular plate.
The vector does not necessarily have unit length.

```

#### I/O

```
Given:

v1,
v2,
v3         are 3-vectors constituting the vertices of
a triangular plate.

[3,1] = size(v1); double = class(v1)
[3,1] = size(v2); double = class(v2)
[3,1] = size(v3); double = class(v3)

the call:

[normal] = cspice_pltnrm(v1, v2, v3,)

returns:

normal     is an outward normal vector of the plate defined by
the input vertices. The order of the vertices is
used to determine the choice of normal direction:
the normal vector is

( V2 - V1 ) x ( V3 - V2 )

[3,1] = size(normal); double = class(normal)

```

#### 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.

Example(1):

Compute an outward normal of an equilateral triangle lying
in the X-Y plane and centered at the origin.

function pltnrm_t

s = sqrt(3.0)/2;

v1 = [  s,  -0.5,  0.0]';
v2 = [ 0.0,  1.0,  0.0]';
v3 = [ -s,  -0.5,  0.0]';

normal = cspice_pltnrm( v1, v2, v3 );

fprintf ( 'NORMAL = %18.11e %18.11e %18.11e\n', ...
normal(1), normal(2), normal(3)      );

Matlab outputs:

NORMAL =  0.00000000000e+00  0.00000000000e+00  2.59807621135e+00

```

#### Particulars

```
This routine saves computation time by not scaling the output
vector to unit length. The caller can scale the vector using
the routine cspice_vhat.

```

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

MICE.REQ
DSK.REQ

```

#### Version

```
-Mice Version 1.0.0, 17-MAR-2016, EDW (JPL), NJB (JPL)

```

#### Index_Entries

```
compute normal vector of triangular plate from vertices

```
`Wed Apr  5 18:00:34 2017`