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# 16.2. Povray

The Persistence of Vision Raytracer is a high-quality, totally free tool for creating stunning three-dimensional graphics.

Ray-tracing is a rendering technique that calculates an image of a scene by simulating the way rays of light travel in the real world. However it does its job backwards. In the real world, rays of light are emitted from a light source and illuminate objects. The light reflects off of the objects or passes through transparent objects. This reflected light hits our eyes or perhaps a camera lens. Because the vast majority of rays never hit an observer, it would take forever to trace a scene.

These kind of applications can be easily made parrallel by using pvmpovray. Pvmpovray expects to working on a Beowulf style cluster and spread it's load to other nodes using pvm. The openMosix way of doing this is the same, however we just do this on 1 machine and have openMosix do the load spreading work fo you !

A GREAT Howto on PVM Povray will show you how to setup PVMPovray. Below is a small summary.

    $ cd pvmpov3_1g_2
    $ tar xfz ../povuni_s.tgz
    $ tar xfz ../povuni_d.tgz
    $ ./inst-pvm
    Trying to apply the patch.
    Searching for rejected files
    $

Now compile with aimk ( which is a wrapper script provided by the pvm rpm , buth which probably won't be in your path.(some of the readers might remember aimk from other platforms / applications )

If you are on a RH 8.0 box id moved libpng and zlib to .notused .. This in order to prevent version issues .. with other libpng and zlib versions.

    export PATH=$PATH:/usr/share/pvm3/lib
    export PVMROOt=/usr/share/pvm3

I then run aimk newunix. Then we start pvm and quit it. The daemon stays active..

And a last thing that is not known by a novice pvm user is that pvm does use its own paths, and you have to put pvmpov either in that path or launch it with the complete pathname.

    [root@dhcp71 povray31]# /usr/local/bin/pvmpov -L
    /usr/src/povray/pvmpov3_1g_2/povray31/include/ +Iskyvase.pov
    +Oskyvase.tga +NT16 +NW64 +NH64 +v +w1024 +h768
    Persistence of Vision(tm) Ray Tracer Version 3.1g.Linux.gcc
      This is an unofficial version compiled by:
      Jakob Flierl  - PVMPOV Version 3.1g.2
      The POV-Ray Team(tm) is not responsible for supporting this version.
    Copyright 1999 POV-Ray Team(tm)
    Never found section  in file
    /usr/src/povray/pvmpov3_1g_2/povray31/include/.
    Initializing PVMPOV
      Spawning /usr/local/bin/pvmpov with 16 PVM tasks on 1 hosts...
      ...16 PVM tasks successfully spawned.
      Waiting up to 120s for first slave to start...
      Slave 0 successfully started.
    Parsing Options
      Input file: skyvase.pov (compatible to version 3.1)
      Remove bounds........On  Split unions........Off
      Library paths: /usr/local/lib/povray31 /usr/local/lib/povray31/include
    Output Options
      Image resolution 1024 by 768 (rows 1 to 768, columns 1 to 1024).
      Output file: skyvase.tga, 24 bpp PNG
      Graphic display.....Off
      Mosaic preview......Off
      CPU usage histogram.Off
      Continued trace.....Off  Allow interruption...On  Pause when
    done.....Off
      Verbose messages.....On
    Tracing Options
      Quality:  9
      Bounding boxes.......On  Bounding threshold: 25
      Light Buffer.........On  Vista Buffer.........On
      Antialiasing........Off
      Radiosity...........Off
    Animation Options
      Clock value....   0.000  (Animation off)
    PVM Options
      Block Width....      64  Block Height...      64
      PVM Tasks......      16
      PVM Nice.......       5
      PVM Arch.......
      PVM Slave...... /usr/local/bin/pvmpov
      PVM WorkingDir. /usr/src/povray/pvmpov3_1g_2/povray31
    Redirecting Options
      All Streams to console..........On
      Debug Stream to console.........On
      Fatal Stream to console.........On
      Render Stream to console........On
      Statistics Stream to console....On
      Warning Stream to console.......On

    Starting frame 0...
     Slave 1 at dhcp71.office.be.stone-it.com successfully started.
     Slave 2 at dhcp71.office.be.stone-it.com successfully started.
     Slave 3 at dhcp71.office.be.stone-it.com successfully started.
     Slave 4 at dhcp71.office.be.stone-it.com successfully started.
     Slave 5 at dhcp71.office.be.stone-it.com successfully started.
     Slave 6 at dhcp71.office.be.stone-it.com successfully started.
     Slave 7 at dhcp71.office.be.stone-it.com successfully started.
     Slave 8 at dhcp71.office.be.stone-it.com successfully started.
     Slave 9 at dhcp71.office.be.stone-it.com successfully started.
     Slave 10 at dhcp71.office.be.stone-it.com successfully started.
     Slave 11 at dhcp71.office.be.stone-it.com successfully started.
     Slave 12 at dhcp71.office.be.stone-it.com successfully started.
     Slave 13 at dhcp71.office.be.stone-it.com successfully started.
     Slave 14 at dhcp71.office.be.stone-it.com successfully started.
     Slave 15 at dhcp71.office.be.stone-it.com successfully started.
      0:00:53 86.46 of blocks complete.Not using dhcp71.office.be.stone-it.com
    for reassignment (77%)
      0:00:53 86.98 of blocks complete.Not using dhcp71.office.be.stone-it.com
    for reassignment (67%)
    Not using dhcp71.office.be.stone-it.com for reassignment (86%)
    Not using dhcp71.office.be.stone-it.com for reassignment (85%)
      0:00:55 89.06 of blocks complete.   640 of  768 lines finished (in frame
    0).Not using dhcp71.office.be.stone-it.com for reassignment (65%)
      0:00:56 91.67 of blocks complete.Not using dhcp71.office.be.stone-it.com
    for reassignment (72%)
      0:00:56 92.71 of blocks complete.Not using dhcp71.office.be.stone-it.com
    for reassignment (80%)
      0:00:57 93.75 of blocks complete.
    Slave at dhcp71.office.be.stone-it.com has exited.
      0:00:57 94.79 of blocks complete.
    Slave at dhcp71.office.be.stone-it.com has exited.

    Slave at dhcp71.office.be.stone-it.com has exited.
      0:00:58 95.83 of blocks complete.
    Slave at dhcp71.office.be.stone-it.com has exited.
      0:00:58 96.35 of blocks complete.   672 of  768 lines finished (in frame
    0).Not using dhcp71.office.be.stone-it.com for reassignment (77%)

    Slave at dhcp71.office.be.stone-it.com has exited.
      0:00:58 97.14 of blocks complete.   688 of  768 lines finished (in frame
    0).
    Slave at dhcp71.office.be.stone-it.com has exited.
      0:00:59 97.92 of blocks complete.
    Slave at dhcp71.office.be.stone-it.com has exited.
      0:00:60 98.44 of blocks complete.   704 of  768 lines finished (in frame
    0).
    Slave at dhcp71.office.be.stone-it.com has exited.
      0:01:03 100.00 of blocks complete.   768 of  768 lines finished (in
    frame 0).
    Finishing frame 0...rtw. 768

    Waiting for remaining slave stats.

    PVM Task Distribution Statistics:
               host name  [ done ] [ late ]           host name  [ done ] [
    late ]
    dhcp71.office.be.stone-it.com  [ 5.21%] [
    0.00%]dhcp71.office.be.stone-it.com  [ 7.81%] [ 0.07%]
    dhcp71.office.be.stone-it.com  [ 8.85%] [
    1.17%]dhcp71.office.be.stone-it.com  [ 4.69%] [ 0.00%]
    dhcp71.office.be.stone-it.com  [ 8.85%] [
    0.98%]dhcp71.office.be.stone-it.com  [ 4.17%] [ 0.00%]
    dhcp71.office.be.stone-it.com  [ 5.21%] [
    0.00%]dhcp71.office.be.stone-it.com  [ 8.33%] [ 0.52%]
    dhcp71.office.be.stone-it.com  [ 5.21%] [
    0.00%]dhcp71.office.be.stone-it.com  [ 5.73%] [ 0.72%]
    dhcp71.office.be.stone-it.com  [ 7.29%] [
    2.73%]dhcp71.office.be.stone-it.com  [ 4.17%] [ 0.00%]
    dhcp71.office.be.stone-it.com  [ 5.21%] [
    0.00%]dhcp71.office.be.stone-it.com  [ 6.77%] [ 0.13%]
    dhcp71.office.be.stone-it.com  [ 4.69%] [
    0.00%]dhcp71.office.be.stone-it.com  [ 7.81%] [ 0.00%]

    POV-Ray statistics for finished frames:
    skyvase.pov Statistics (Partial Image Rendered), Resolution 1024 x 768
    ----------------------------------------------------------------------------
    Pixels:          303104   Samples:          303104   Smpls/Pxl: 1.00
    Rays:           1192710   Saved:                 0   Max Level: 0/5
    ----------------------------------------------------------------------------
    Ray->Shape Intersection          Tests       Succeeded  Percentage
    ----------------------------------------------------------------------------
    Cone/Cylinder                  1842227          900504     48.88
    CSG Intersection               2742731          323346     11.79
    CSG Union                      1801008          521692     28.97
    Plane                         20223278        11233348     55.55
    Quadric                        1801008         1196533     66.44
    Sphere                         1801008          461786     25.64
    Bounding Object                1842227          900504     48.88
    ----------------------------------------------------------------------------
    Calls to Noise:            1201944   Calls to DNoise:        2108954
    ----------------------------------------------------------------------------
    Shadow Ray Tests:          2856188   Succeeded:                85620
    Reflected Rays:             889606
    ----------------------------------------------------------------------------
    Smallest Alloc:                  9 bytes   Largest:            20508
    Peak memory used:          5643343 bytes
    ----------------------------------------------------------------------------
    Time For Trace:    0 hours  1 minutes   7.0 seconds (67 seconds)
        Total Time:    0 hours  1 minutes   7.0 seconds (67 seconds)

As you can see the application was splitted into differen parts and run separatly, openMosix then did the job of balancing the load to other machines.

I had good results with 2 to 3 times the the number of cpu's I had available

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