[Radiance-general] Reduce rtrace runtime

[Greg Ward]

Computing seven bounces (-ab 7) is very expensive, even for a small number of points.  You end up filling the indirect irradiance cache, which takes some time even on 4 processors.  I would recommend either reducing the number of bounces, or taking advantage of a path tracing approach like so:

	rtrace -w -h -I -ab 7 -n 4  -ad 2048 -as 0 -aa 0 -lw 1e-5 -lr -10 -u+ office.oct < points.inp

Setting -aa 0 and -lw 1e-4 limits the number of paths to roughly 100,000 per point, which should run pretty quickly while maintaining accuracy.

Best,
-Greg


> From: Jia Hu <hujia06 at gmail.com>
> Date: August 30, 2010 6:11:21 PM PDT
> 
> Hello experts:
>  
> I hope to calculate illuminance at 4 points in a office under four 100 sky conditions (each condition will generate four illuminance values). I run rtrace in a  computer with 4 processors and use: rtrace -w -h -I -ab 7 -n 4  -af cachingFile.ca -ad 2048 -as 512 -aa 0.10 office.oct < points.inp | rcalc -e '$1=47.4*$1+ 120*$2+11.6*$3'>> output.out.  
>  
> I tried to run it but it took long time. My question is that whether there are ways of improving the rtrace command to reduce the runtime?
>  
> Cheers,
> Jia