| dskn02_c |
|
Table of contents
Procedure
dskn02_c ( DSK, type 2, compute normal vector for plate )
void dskn02_c ( SpiceInt handle,
ConstSpiceDLADescr * dladsc,
SpiceInt plid,
SpiceDouble normal[3] )
AbstractCompute the unit normal vector for a specified plate from a type 2 DSK segment. Required_ReadingDAS DSK KeywordsDAS DSK FILES Brief_I/OVARIABLE I/O DESCRIPTION -------- --- -------------------------------------------------- handle I DSK file handle. dladsc I DLA descriptor. plid I Plate ID. normal O Plate's unit normal vector. Detailed_Input
handle is the handle of a DSK file containing a type 2
segment from which data are to be fetched.
dladsc is the DLA descriptor associated with the segment
from which data are to be fetched.
plid is the plate ID. Plate IDs range from 1 to NP
(the number of plates).
Detailed_Output
normal is the normal vector associated with the plate
designated by `plid'. 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.
Parameters
See the header file
SpiceDLA.h
for declarations of DLA descriptor sizes and documentation of the
contents of DLA descriptors.
See the header file
SpiceDSK.h
for declarations of DSK descriptor sizes and documentation of the
contents of DSK descriptors.
See the header file
SpiceDSK.h
for declarations of DSK data type 2 (plate model) parameters.
Exceptions
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.
FilesSee input argument `handle'. ParticularsNone. Examples
The numerical results shown for this example may differ across
platforms. The results depend on the SPICE kernels used as
input, the compiler and supporting libraries, 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.
/.
Program dskn02_ex1
./
#include <stdio.h>
#include "SpiceUsr.h"
int main()
{
/.
Constants
./
#define PBUFSIZ 10000
#define FILSIZ 256
/.
Local variables
./
SpiceBoolean found;
SpiceChar dsk [ FILSIZ ];
SpiceDLADescr dladsc;
SpiceDouble normal [3];
SpiceDouble verts [3][3];
SpiceInt handle;
SpiceInt i;
SpiceInt j;
SpiceInt n;
SpiceInt np;
SpiceInt nread;
SpiceInt nv;
SpiceInt nvtx;
SpiceInt plates[PBUFSIZ][3];
SpiceInt plix;
SpiceInt remain;
SpiceInt start;
/.
Prompt for name of DSK and open file for reading.
./
prompt_c ( "Enter DSK name > ", FILSIZ, dsk );
dasopr_c ( dsk, &handle );
dlabfs_c ( handle, &dladsc, &found );
if ( !found )
{
setmsg_c ( "No segment found in file #." );
errch_c ( "#", dsk );
sigerr_c ( "SPICE(NOSEGMENT)" );
}
/.
Get segment vertex and plate counts.
./
dskz02_c ( handle, &dladsc, &nv, &np );
printf ( "\n"
"Number of vertices: %d\n"
"Number of plates: %d\n",
(int)nv,
(int)np );
/.
Display the vertices of each of the first 5 plates.
./
remain = mini_c ( 2, 5, np );
start = 1;
while ( remain > 0 )
{
/.
`nread' is the number of plates we"ll read on this
loop pass.
./
nread = mini_c ( 2, PBUFSIZ, remain );
dskp02_c ( handle, &dladsc, start, nread, &n, plates );
for ( i = 0; i < nread; i++ )
{
plix = start + i;
/.
Read the vertices of the current plate.
./
for ( j = 0; j < 3; j++ )
{
dskv02_c ( handle, &dladsc, plates[i][j],
1, &nvtx,
( SpiceDouble(*)[3] )(verts[j]) );
}
/.
Display the vertices of the current plate:
./
printf ( "\n"
" Plate number: %d\n"
" Vertex 1: ( %16.8e %16.8e %16.8e )\n"
" Vertex 2: ( %16.8e %16.8e %16.8e )\n"
" Vertex 3: ( %16.8e %16.8e %16.8e )\n",
(int)plix,
verts[0][0], verts[0][1], verts[0][2],
verts[1][0], verts[1][1], verts[1][2],
verts[2][0], verts[2][1], verts[2][2] );
/.
Display the normal vector of the current plate:
./
dskn02_c ( handle, &dladsc, plix, normal );
printf( " Normal: ( %16.8e %16.8e %16.8e )\n",
normal[0], normal[1], normal[2] );
}
start = start + nread;
remain = remain - nread;
}
/.
Close the kernel. This isn't necessary in a stand-
alone program, but it's good practice in subroutines
because it frees program and system resources.
./
dascls_c ( handle );
return ( 0 );
}
When this program was executed on a Mac/Intel/cc/64-bit
platform, using the DSK file named phobos512.bds, the output
was:
Enter DSK name > 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 )
RestrictionsSee -Exceptions section. Literature_ReferencesNone. Author_and_InstitutionN.J. Bachman (JPL) J. Diaz del Rio (ODC Space) Version
-CSPICE Version 1.0.2, 10-AUG-2021 (JDR)
Edited the header to comply with NAIF standard. Updated
code example to reduce the number of plates whose vertices are
shown on output and to remove unnecessary include files.
-CSPICE Version 1.0.1, 27-JAN-2016 (NJB)
Edit to example program to use "%d" with explicit casts
to int for printing SpiceInts with printf.
Updated header -Detailed_Output and -Index_Entries
sections.
-CSPICE Version 1.0.0, 03-JUN-2010 (NJB)
Index_Entriescompute normal vector for a type 2 DSK plate compute normal vector from DSK type 2 plate id |
Fri Dec 31 18:41:04 2021