Table of contents
CSPICE_DSKN02 computes the unit normal vector for a specified plate from
a type 2 DSK segment.
Given:
handle the handle of a DSK file containing a type 2 segment
from which data are to be fetched.
[1,1] = size(handle); int32 = class(handle)
dladsc the DLA descriptor associated with the segment from
which data are to be fetched.
[SPICE_DLA_DSCSIZ,1] = size(dladsc)
int32 = class(dladsc)
plid the plate ID.
[1,1] = size(plid); int32 = class(plid)
Plate IDs range from 1 to NP (the number of plates in the
segment identified by `dladsc').
the call:
[normal] = cspice_dskn02( handle, dladsc, plid )
returns:
normal the normal vector associated with the plate designated
by `plid'.
[3,1] = size(normal); double = class(normal)
The direction of `normal' is determined by the order of the
plate's vertices; the vertices are presumed to be ordered in
the right-handed (counterclockwise) sense about the normal
direction. If the plate's vertices are `v1', `v2', `v3', then
`normal' points in the direction
(v2 - v1) x ( v3 - v2 )
where 'x' represents the cross product operator.
The vector `normal' is expressed in the body-fixed
reference frame of the segment designated by `dladsc'.
The center of this frame is the origin of the cartesian
coordinate system in which the vertices are expressed.
Note that the frame center need not coincide with the
central body of the segment. Units are km.
The vector has magnitude 1.
If an error occurs on the call, `normal' is undefined.
See the parameter definitions file
MiceDLA.m
for declarations of DLA descriptor sizes and documentation of the
contents of DLA descriptors.
See the parameter definitions file
MiceDSK.m
for declarations of DSK descriptor sizes and documentation of the
contents of DSK descriptors.
See the parameter definitions file
MiceDSK.m
for declarations of DSK data type 2 (plate model) parameters.
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.
1) Look up all the vertices associated with each plate
of the model contained in a specified type 2 segment. For each
of the first 5 plates, display the plate's vertices and normal
vector.
For this example, we'll show the context of this look-up:
opening the DSK file for read access, traversing a trivial,
one-segment list to obtain the segment of interest.
Example code begins here.
function dskn02_ex1
%
% Constants
%
PBUFSIZ = 10000;
%
% Initial values
%
verts = zeros(3,3);
%
% Prompt for the name of the file to search.
%
dsk = input( 'Name of DSK file > ', 's' );
%
% Open the DSK file for read access.
% We use the DAS-level interface for
% this function.
%
handle = cspice_dasopr( dsk );
%
% Begin a forward search through the
% kernel, treating the file as a DLA.
% In this example, it's a very short
% search.
%
[dladsc, found] = cspice_dlabfs( handle );
if ~found
%
% We arrive here only if the kernel
% contains no segments. This is
% unexpected, but we're prepared for it.
%
fprintf( 'No segments found in DSK file %s\n', dsk )
return
end
%
% If we made it this far, `dladsc' is the
% DLA descriptor of the first segment.
%
% Get segment vertex and plate counts.
%
[nv, np] = cspice_dskz02( handle, dladsc );
fprintf( '\n' )
fprintf( 'Number of vertices: %d\n', nv )
fprintf( 'Number of plates: %d\n', np )
%
% Display the vertices of each of the first 5 plates.
%
remain = min(np, 5);
start = 1;
while (remain > 0 )
%
% `nread' is the number of plates we"ll read on this
% loop pass. Set `nread' to the minimum of PBUFSIZ
% and `remain'.
%
nread = min(PBUFSIZ, remain);
plates = cspice_dskp02( handle, dladsc, start, nread );
for i = 1:(nread)
plix = start + i - 1;
%
% Read the vertices of the current plate.
%
for j = 1:3
verts(j,:) = cspice_dskv02( handle, ...
dladsc, plates(j,i), 1 );
end
%
% Display the vertices of the ith plate:
%
fprintf( '\n' )
fprintf( 'Plate number: %d\n', plix )
for j = 1:3
fprintf( ' Vertex %d: ( %16.8e %16.8e %16.8e )\n', ...
j, verts(j,:) )
end
%
% Display the normal vector of the current plate:
%
normal = cspice_dskn02( handle, dladsc, plix );
fprintf( ' Normal: ( %16.8e %16.8e %16.8e )\n', normal )
end
start = start + nread;
remain = remain - nread;
end
%
% Close file.
%
cspice_dascls( handle )
When this program was executed on a Mac/Intel/Octave5.x/64-bit
platform, using the DSK file named phobos512.bds, the output
was:
Name of DSK file > phobos512.bds
Number of vertices: 1579014
Number of plates: 3145728
Plate number: 1
Vertex 1: ( -6.77444000e+00 6.26815000e+00 6.01149000e+00 )
Vertex 2: ( -6.76238000e+00 6.25728000e+00 6.02556000e+00 )
Vertex 3: ( -6.75710000e+00 6.27754000e+00 6.02096000e+00 )
Normal: ( -5.81973770e-01 3.21285613e-01 7.47048918e-01 )
Plate number: 2
Vertex 1: ( -6.77444000e+00 6.26815000e+00 6.01149000e+00 )
Vertex 2: ( -6.77973000e+00 6.24790000e+00 6.01610000e+00 )
Vertex 3: ( -6.76238000e+00 6.25728000e+00 6.02556000e+00 )
Normal: ( -5.81456950e-01 3.21988310e-01 7.47148809e-01 )
Plate number: 3
Vertex 1: ( -6.77973000e+00 6.24790000e+00 6.01610000e+00 )
Vertex 2: ( -6.76768000e+00 6.23701000e+00 6.03019000e+00 )
Vertex 3: ( -6.76238000e+00 6.25728000e+00 6.02556000e+00 )
Normal: ( -5.81597068e-01 3.22641957e-01 7.46757671e-01 )
Plate number: 4
Vertex 1: ( -6.77973000e+00 6.24790000e+00 6.01610000e+00 )
Vertex 2: ( -6.78499000e+00 6.22762000e+00 6.02070000e+00 )
Vertex 3: ( -6.76768000e+00 6.23701000e+00 6.03019000e+00 )
Normal: ( -5.83129010e-01 3.20560704e-01 7.46459237e-01 )
Plate number: 5
Vertex 1: ( -6.78499000e+00 6.22762000e+00 6.02070000e+00 )
Vertex 2: ( -6.77299000e+00 6.21674000e+00 6.03482000e+00 )
Vertex 3: ( -6.76768000e+00 6.23701000e+00 6.03019000e+00 )
Normal: ( -5.83664048e-01 3.23060196e-01 7.44962005e-01 )
None.
1) If the input handle is invalid, an error is signaled by a
routine in the call tree of this routine.
2) If a file read error occurs, the error is signaled by a
routine in the call tree of this routine.
3) If the input DLA descriptor is invalid, the effect of this
routine is undefined. The error *may* be diagnosed by
routines in the call tree of this routine, but there are no
guarantees.
4) If `plid' is less than 1 or greater than the number of plates in
the segment, the error SPICE(INDEXOUTOFRANGE) is signaled by a
routine in the call tree of this routine.
5) This routine does not check for linear independence of the
plate's edges. The plate model is assumed to be geometrically
valid.
6) If any of the input arguments, `handle', `dladsc' or `plid',
is undefined, an error is signaled by the Matlab error
handling system.
7) If any of the input arguments, `handle', `dladsc' or `plid',
is not of the expected type, or it does not have the expected
dimensions and size, an error is signaled by the Mice
interface.
See input argument `handle'.
See -Exceptions section.
DAS.REQ
DSK.REQ
MICE.REQ
None.
N.J. Bachman (JPL)
J. Diaz del Rio (ODC Space)
E.D. Wright (JPL)
-Mice Version 1.1.0, 21-JUL-2020 (EDW) (JDR)
Fixed typos in code example.
Edited the header to comply with NAIF standard. Updated
code example to prompt for the input DSK file and reduce the
number of plates whose vertices are shown on output.
Added -Parameters, -Exceptions, -Files, -Restrictions,
-Literature_References and -Author_and_Institution sections.
Eliminated use of "lasterror" in rethrow.
Removed reference to the function's corresponding CSPICE header from
-Required_Reading section.
-Mice Version 1.0.0, 06-MAY-2014 (NJB) (EDW)
compute normal vector for a type 2 DSK plate
compute normal vector from DSK type 2 plate id
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