Index of Functions: A B C D E F G H I J K L M N O P Q R S T U V W X
Index Page dskn02_c
Table of contents
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
       dskn02_c ( DSK, type 2, compute normal vector for plate )

       void dskn02_c ( SpiceInt               handle,
                       ConstSpiceDLADescr   * dladsc,
                       SpiceInt               plid,
                       SpiceDouble            normal[3] )
#### Abstract
       Compute the unit normal vector for a specified plate 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.
       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.
#### Files
       See input argument `handle'.
#### Particulars
       None.
#### 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 )
#### Restrictions
       See -Exceptions section.
#### Literature_References
       None.
#### Author_and_Institution
       N.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_Entries
       compute normal vector for a type 2 DSK plate
       compute normal vector from DSK type 2 plate id
#### Link to routine dskn02_c source file dskn02_c.c

    Fri Dec 31 18:41:04 2021