[Radiance-general] ambient accuracy parameter

[Gregory J. Ward]

Just wanted to chime in on this thread.  The -aa 0 setting is  
appropriate when you have a lot of small geometry that isn't safe to  
leave out of the ambient calculation (using the -ae or -aE options),  
or for special applications such as mkillum or rtcontrib.  Turning  
off the ambient cache is NOT a good idea when what you care about is  
individual ray accuracy, such as when you are using rtrace to  
evaluate radiance or irradiance values in a space.  It can be done  
with -aa 0, but you have to pay close attention to your other  
parameter settings (such as -ad, -as, -lw, and -lr) and alter them  
appropriately.  The -ar setting has no effect with -aa 0.  Ditto for - 
aw.

-Greg

> From: Marija Cvetkovic <cveleglg at bankerinter.net>
> Date: December 26, 2006 1:30:46 AM PST
>
> Hi,
>
> I've been reading some previous posts related to ambient parameters  
> settings and I have some questions.
>
> When it is recommendable to use -aa 0 value? If I understand this  
> parameter well, 0 value turns off irradiance caching, so we can use  
> it when caching isn't needed (mkillum calculation for venetian  
> blinds or rtcontrib).
> When we set -aa 0, does -ar have influence on minimum sampling  
> distance, since: min sampling distance = max scene dimension* aa/ar.
>
> When I run a rtrace calculation with -aa 0, calculation time is  
> much shorter than with -aa 0.1. Why?
>
> Have a nice holidays :)
> Marija.