Am 27.09.2011 23:52, schrieb Cousin Ricky:
> Thomas de Groot<tenDOTlnDOTretniATtoorgedDOTt>  wrote:
>
>>       radiosity {
>>         #if (RadSave)
>>           pretrace_start 0.08
>>           pretrace_end   0.004
>>           count 50, 1000
>>           error_bound 0.5
>>           always_sample on
>
> In his Radiosity Voodoo articles (povray.text.tutorials), clipka recommends
> setting always_sample to off.

Those recommendations are for using radiosity in a single render. When 
using a simplified scene to generate & save radiosity data, to be loaded 
& used later in a separate render, "always_sample on" is ok; the 
pre-render's main phase is likely to suffer artifacts, but it is 
discarded anyway, and this way it's still good for something (namely to 
serve as yet another radiosity pretrace step).

>
>>         #else
>>           pretrace_start 1
>>           pretrace_end   1
>>           count 50, 100
>>           error_bound 1
>
> In 3.6, error_bound should be the same for both passes, otherwise the 2nd pass
> would take eons.  I haven't tested this in 3.7.

It shouldn't be set /lower/ than in the first pass, but a higher value 
should be ok. Some care is recommended though: Increasing error_bound 
also increases the risk of light "leaking" through walls in corners.

>>           always_sample off
>>         #end  //of RadSave
>>         brightness 1
>>         recursion_limit 2
>>         nearest_count 10, 5
>
> In his Radiosity Voodoo articles, clipka recommends setting nearest_count to 1,
> especially during the final render.  However, the current documentation suggests
> that this would have poor results.  Although I can't recall the details, I
> remember that I didn't get satisfactory results by tweaking this.

I'm not so sure about this recommendation any longer. For the main pass 
in a 2-pass approach it doesn't actually matter much: In the main pass 
pretrace, a pretrace_start and pretrace_end setting of 1 will make sure 
that at most one single additional sample will be taken (if any 
pretracing is done at all; I'm not perfectly sure about that right now), 
which doesn't make much of a difference; and with always_sample off the 
nearest_count setting is irrelevant during the render proper anyway.

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