I already made this scene some time ago but i thought this might be a 
good occasion to post it since we have just released MegaPOV 1.2.1 which 
includes the radiosity patches used.

This image demonstrates the use of the adaptive pretrace and adaptive 
error_bound patches in a large render of a detailed scene.  One major 
problem of such renders is that they tend to be very slow at large size 
since a lot of additional samples are taken in the final pass which also 
results in a raise of memory use.  The adaptive error_bound gives better 
control over this - in this case there were only 19 radiosity samples 
taken in the final pass so you can predict the render time and results 
much better from a small size test render.

The adaptive pretrace can reduce the pretrace time in a scene with large 
areas only requiring very few samples (like the sky here).  However you 
have to use a low pretrace_start to avoid areas to be completely skipped 
by the pretrace.  The pretrace time here was 4 hours (final pass time 
was 13 hours for 6400 x 3600).

The radiosity settings used are:

   radiosity {
     pretrace_start 0.006
     pretrace_end   0.0015
     adaptive 1
     count 100
     nearest_count 3
     error_bound { 0.8 adaptive 1.5, 20 }
     recursion_limit 1
     low_error_factor 0.2
     gray_threshold 0.0
     minimum_reuse 0.015
     brightness 0.85
     always_sample off
   }

Christoph

-- 
POV-Ray tutorials, include files, Landscape of the week:
http://www.tu-bs.de/~y0013390/ (Last updated 24 Jul. 2005)
MegaPOV with mechanics simulation: http://megapov.inetart.net/

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