[...] PVMPOV and radiosity:

Radiosity is currently not working with PVMPOV; the resulting images look like
mosaics. There's a currently only a workaround suggested by Andreas Dilger:

You must create a .rca file for the whole image [when rendering with the
radiosity option turned on], which I did manually by running
"pvmpov -n +qr +d +i <scene>.pov" and stopping the rendering when the mosaic
preview is complete, to give me <scene>.rca. Then I started a new
"pvmpov +c +qr +d +i <scene>.pov +nt2" on my 2 CPU system, and it rendered
the same image as letting "pvmpov -n +qr +d +i <scene>.pov" finish on 1 CPU.
The <scene>.rca file was readable by both slave systems because they were local,
but it would also be possible to use NFS for this, like normal PVMPOV.
This is some work to do manually, but it will ensure that the radiosity
will work properly with PVMPOV.

[for programmers only:]
What needs to be done now is to have the PVMPOV master run the mosaic
preview for radiosity before the slave tasks start.  It looks like this
could be done in pvm.c:PvmStartFrame(), but the current design of the
master doesn't allow it to do any rendering because it does not parse
the scene, so it would need to be reworked to do this.

In the old PVMPOV 2.2 design, the master did the parsing of the scene
file to ensure that the syntax was correct.  I think this is the better
design.  If radiosity is used, the master will render the preview before
the rendering is started on the slaves, so the .rca file is available.
If the master does the parsing, then it can also send the data to the
slaves via the POB binary file format through PVM (no NFS needed) so we
don't waste the time spent parsing the scene at the master.

I think what needs to be done is modify povray.c so it doesn't call
Pvm_Master_Control() instead of FrameRender() in povray.c:398.  Then
FrameRender() should be modified to work with PVMPOV code, replacing
PvmStartFrame() entirely.  This will mean that PVMPOV will render one
frame at a time, which is OK I think, because it means that some of
the problems with PVMPOV 3.x will be fixed, like post-scene shellouts.
I think it will also make PVMPOV less complex also, because it only
has to work on 1 frame at a time.
