Radiance rpiece program

RPIECE(1)                                                            RPIECE(1)

NAME

       rpiece - render pieces of a RADIANCE picture

SYNOPSIS

       rpiece  [  -v ][ -x xres ][ -y yres ][ -X xdiv ][ -Y ydiv ][ -F|R sync-
       file ][ -T timelim ] [ $EVAR ] [ @file ] [ rpict options ]  -o  picture
       octree

DESCRIPTION

       Rpiece  renders  a RADIANCE picture a piece at a time, calling rpict(1)
       to do the actual work.  This is useful for running multiple rpict  pro-
       cesses  on  cooperating machines to render a single picture, which is a
       shared file specified with the -o option.  The overall  picture  dimen-
       sions will be xres by yres (or smaller, depending on the -pa option and
       other view options), and the picture will be rendered in xdiv  by  ydiv
       pieces.

       There are two basic methods for telling rpiece which piece(s) of a pic-
       ture to render.  The explicit method is to write on the standard  input
       the X and Y position of the desired piece(s), where X runs from zero to
       xdiv-1 and Y runs from zero to ydiv-1.  (The lower left piece of a pic-
       ture corresponds to (0,0) in this system.)  Alternatively, the implicit
       specification method uses a synchronization  file  to  determine  which
       piece  is  to be rendered next.  Specified with the -F option, syncfile
       initially contains the values for xdiv and  ydiv,  so  the  -X  and  -Y
       options  are unnecessary.  (However, they are used if syncfile does not
       exist.)  The first rpiece process puts a lock on syncfile and  modifies
       its  contents before starting work on the first piece of the image.  It
       writes the X and Y position of the piece it will work on, so  the  next
       rpiece  process to modify syncfile will start on the next piece.  (When
       it finishes with its piece, it appends the index to the  end  of  sync-
       file.)   This  procedure  continues  until  all the pieces are done, at
       which point all of the rpiece processes will terminate.

       The -R option may be used instead of -F if some of the pieces were  not
       properly  finished  by  previous  (killed) runs of rpiece.  This option
       should be used by at most one rpiece process,  which  must  be  started
       first and with no other rpiece processes running or else it will reren-
       der the same pieces other  processes  have  begun.   Once  the  recover
       process  is  started, you may start other rpiece processes using the -F
       option to run simultaneously.  If some processes die during  execution,
       leaving one or more half-finished pieces in the picture even though the
       other processes think the work is done, you may  run  a  single  rpiece
       with the -R option by itself to repair the holes.

       The -v flag switches on verbose mode, where rpiece reports to the stan-
       dard output after each piece begins and after each piece is finished.

       Options may be given on the command line and/or read from the  environ-
       ment and/or read from a file.  A command argument beginning with a dol-
       lar sign ('$') is immediately replaced by the  contents  of  the  given
       environment  variable.   A  command  argument beginning with an at sign
       ('@') is immediately replaced by the contents of the given file.

EXAMPLE

       First rpiece process is started on the machine "goober":

         goober% echo 1 8 > syncfile
         goober% echo -F syncfile -x 1024 -y 1024 -vf view -o picture octree >
         args
         goober% rpiece @args &

       Second rpiece processes is started on the machine "sucker":

         sucker% rpiece @args &

NOTES

       Due  to  NFS  file  buffering,  the network lock manager is employed to
       guarantee consistency in the output file  even  though  non-overlapping
       writes  are  used.   This would tend to slow the process down if rpiece
       were to wait for this I/O to  complete  before  starting  on  the  next
       piece,  so  rpiece  forks separate processes to hang around waiting for
       I/O completion.  The number of processes thus designated is set by  the
       MAXFORK  macro in the program (compiled in the src/util directory).  If
       the fork call is slow on a system, it may actually  be  better  to  set
       MAXFORK  to  zero.   In other cases, the network lock manager may be so
       slow that this value should be increased to get the best utilization.

       The output picture is not run-length encoded, and can be  quite  large.
       The  approximate size (in kilobytes) can be computed by the simple for-
       mula:

         filesize = xres*yres/256

       Make sure that there is enough space on  the  filesystem  to  hold  the
       entire  picture  before  beginning.   Once the picture is finished, the
       ra_rgbe(1) program with the -r option may  be  used  to  convert  to  a
       run-length   encoded  picture  for  more  efficient  storage,  although
       pfilt(1) or any of the other Radiance picture filters will do the  same
       thing.

       The  ALRM  signal may be used to gracefully terminate an rpiece process
       after it finishes the current piece.  This permits other currently run-
       ning  or  subsequently started rpiece process(es) to continue rendering
       the picture without loss.  The -T option will send the ALRM  signal  to
       rpiece after the specified number of (decimal) hours.  This is the best
       way to force a time limit on the computation,  since  information  will
       not  be  lost, though the process may continue for some time afterwards
       to finish its current piece.

BUGS

       This program may not work on some systems whose  NFS  lock  manager  is
       unreliable.  In particular, some System V derivative UNIX systems often
       have problems with the network lock manager.  If the output  is  scram-
       bled or rpict aborts with some ambient file related problem, you should
       just remove the ambient file and go back to normal rendering.

AUTHOR

       Greg Ward

SEE ALSO

       getinfo(1), pfilt(1), ra_rgbe(1), rpict(1), ximage(1)

RADIANCE                            10/1/98                          RPIECE(1)