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dskv02_c
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Procedure
Abstract
Required_Reading
Keywords
Brief_I/O
Detailed_Input
Detailed_Output
Parameters
Exceptions
Files
Particulars
Examples
Restrictions
Literature_References
Author_and_Institution
Version
Index_Entries

Procedure

   void dskv02_c ( SpiceInt               handle,
                   ConstSpiceDLADescr   * dladsc,
                   SpiceInt               start,
                   SpiceInt               room,
                   SpiceInt             * n,
                   SpiceDouble            vrtces[][3] ) 

Abstract

 
   Fetch vertices from a type 2 DSK segment. 
 

Required_Reading

 
   DAS 
   DSK 
 

Keywords

 
   DAS 
   DSK 
   FILES 
 

Brief_I/O

 
   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. 
 

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.  
 
   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.
 

Detailed_Output

 
   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.
 

Parameters

 
   See the header file
 
       SpiceDLA.h
 

Exceptions

 
   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.
 

Files

 
   See input argument `handle'. 
 

Particulars

 
   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. 
 

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 
      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 )
 
 

Restrictions

 
   None. 
 

Literature_References

 
   None. 
 

Author_and_Institution

 
   N.J. Bachman    (JPL) 
 

Version

   -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)
 

Index_Entries

   return specified vertices from type 2 DSK segment
Wed Apr  5 17:54:32 2017