void dskv02_c ( SpiceInt handle,
ConstSpiceDLADescr * dladsc,
SpiceInt start,
SpiceInt room,
SpiceInt * n,
SpiceDouble vrtces[][3] )
Fetch vertices from a type 2 DSK segment.
DAS
DSK
DAS
DSK
FILES
Variable I/O Description
-------- --- --------------------------------------------------
handle I DSK file handle.
dladsc I DLA descriptor.
start I Start index.
room I Amount of room in output array.
n O Number of vertices returned.
vrtces O Array containing vertices.
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.
start is the ID of the first vertex to be fetched from the
segment designated by `handle' and `dladsc'. The ID
of a vertex is its ordinal position within the
segment. Vertex IDs range from 1 to NV, where NV is
the number of vertices in the segment.
Note that Fortran-style 1-based indexing is used for
vertex IDs because these IDs must be consistent with
the IDs used in DSK files, across all languages
supported by SPICE.
room is the number of vertices that can fit in the output
`vrtces' array: the output array must be large enough
to hold at least 3*room double precision values.
n is the number of vertices fetched to the output array
`vrtces'. `n' is normally in the range
1 : min( NV, room )
If an error occurs on the call, `n' is undefined.
vrtces is a contiguous set of vertices. The returned
vertices are arranged in order of increasing vertex
ID. The IDs of the returned vertices range from
start
to
start + n - 1
Each vertex is a 3-vector. The correspondence of
elements of `vrtces' with the elements of the set of
vertices contained in the segment is:
vrtces[0][0] segment_vertex_set[start][0]
vrtces[0][1] segment_vertex_set[start][1]
vrtces[0][2] segment_vertex_set[start][2]
... ...
vrtces[n-1][0] segment_vertex_set[start+n-1][0]
vrtces[n-1][1] segment_vertex_set[start+n-1][1]
vrtces[n-1][2] segment_vertex_set[start+n-1][2]
The vertices are expressed in the body-fixed
reference frame of the segment designated by `handle'
and `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.
If an error occurs on the call, `vrtces' is
undefined.
See the header file
SpiceDLA.h
1) If the input handle is invalid, the error will be diagnosed by
routines in the call tree of this routine.
2) If a file read error occurs, the error will be diagnosed by
routines 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 `room' is non-positive, the error SPICE(VALUEOUTOFRANGE)
is signaled.
5) If `start' is less than 1 or greater than or equal to the number
of vertices in the segment, the error SPICE(INDEXOUTOFRANGE) is
signaled.
See input argument `handle'.
This routine enables SPICE-based user applications to rapidly
fetch the vertex data from a specified type 2 DSK segment. Using
a large output array generally improves efficiency.
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
plate, 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.
#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 plate.
./
remain = 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 PC/Linux/gcc/64bit
platform, using a DSK file representing a regular icosahedron,
the output was:
Number of vertices: 12
Number of plates: 20
Plate number: 1
Vertex 1: ( 0.00000000e+00 0.00000000e+00 1.17557000e+00 )
Vertex 2: ( 1.05146000e+00 0.00000000e+00 5.25731000e-01 )
Vertex 3: ( 3.24920000e-01 1.00000000e+00 5.25731000e-01 )
Normal: ( 4.91124160e-01 3.56821347e-01 7.94654382e-01 )
Plate number: 2
Vertex 1: ( 0.00000000e+00 0.00000000e+00 1.17557000e+00 )
Vertex 2: ( 3.24920000e-01 1.00000000e+00 5.25731000e-01 )
Vertex 3: ( -8.50651000e-01 6.18034000e-01 5.25731000e-01 )
Normal: ( -1.87592328e-01 5.77350079e-01 7.94654645e-01 )
...
Plate number: 20
Vertex 1: ( 8.50651000e-01 -6.18034000e-01 -5.25731000e-01 )
Vertex 2: ( 0.00000000e+00 0.00000000e+00 -1.17557000e+00 )
Vertex 3: ( 8.50651000e-01 6.18034000e-01 -5.25731000e-01 )
Normal: ( 6.07061680e-01 0.00000000e+00 -7.94654715e-01 )
None.
None.
N.J. Bachman (JPL)
-CSPICE Version 1.0.0, 04-APR-2017 (NJB)
Updated header to refer to "vertex IDs."
27-JAN-2016 (NJB)
Removed references to old header files. Updated
example program. Updated Detailed_Output header
section.
DSKLIB_C Version 1.0.1, 21-APR-2014 (NJB)
The diagram in the Detailed_Output header section showing the
contents of the output `vrtces' array has been corrected.
DSKLIB_C Version 1.0.0 04-JUN-2010 (NJB)
return specified vertices from type 2 DSK segment
Link to routine dskv02_c source file dskv02_c.c
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