[Radiance-general] ambient accuracy parameter

[Marija Cvetkovic]

Hi Martin,

You are talking about ambient resolution (-ar) parameter. For -aa images 
  are better with lower settings of -aa, and maximum recommended value 
is 0.3.
I know what this parameter means for rendering, but my question is when 
value -aa 0 should be used and when not?

Marija

Martin Moeck wrote:
> I use the -aa setting to get a smoother indirect calculation. This is especially important if the -ad parameter is low, i.e., <=512. A high -aa parameter, such as 5000 or whatever, creates a dense grid of indirect/reflected values. You can check that by making two images, one with a low setting of ad and aa, and one with a low setting of ad and a high setting of aa. That will show you immediately what the ambient accuracy parameter is about. The image contains less blotches. 
> 
> Martin Moeck
> 
> 
> -----Original Message-----
> From: radiance-general-bounces at radiance-online.org on behalf of Marija Cvetkovic
> Sent: Tue 12/26/2006 2:30 AM
> To: Radiance general
> Subject: [Radiance-general] ambient accuracy parameter
>  
> 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?
>