[Radiance-general] Mark Stock's work on rendering large models w/o ambient cache

[Gregory J. Ward]

Hi Lars,

Many people have tried small -ad settings with the ambient cache, and  
the universal result is splotchy images.  The reason it works when  
you turn off the ambient cache is that each interreflection  
calculation varies about the correct value randomly, and looks like  
noise in the image because it takes up only one pixel (or with  
downsampling, a fraction of a pixel).  Using -aa (anything positive),  
you spread these high variance values into surrounding pixels, and  
they look like the measles.

-Greg

> From: "Lars Grobe" <grobe at gmx.net>
> Date: February 8, 2006 7:09:29 AM PST
>
> Hi,
>
> Mark did some work on how to get nice results without ambient cache  
> (afaik
> he uses -aa .00 -d 6 -ps 1 and downsamples /4 in pfilt). I tried  
> the same on
> a very large model, but rendering is slow now because the different  
> views
> can't share ambient data. So my suggestion is to keep low -ad and  
> downsample
> as proposed, but cache the fewer ambient values in an ambient file  
> using a
> moderate -aa. Any comments? I wondered why this was not mentioned  
> in the
> studies, am I completely wrong or is it because he simply did not  
> have to
> reuse the ambient values (in a comparision with different ambient  
> settings,
> that would be a bad idea ;-)?
>
> TIA+CU Lars.
>