[Radiance-general] Reduce rtrace runtime

[Greg Ward]

You don't say which way the differences go.  Are they consistently higher or lower?  If higher, then you may be getting a more accurate result from the path tracing method due to Russian-roulette termination.  If the path tracing results are lower, then you may need to decrease the -aw value further.

To answer your earlier quesiton, the -lr setting should be greater (in absolute value) than the -ab setting.  They are similar.  The reason a separate -ab setting is provided is because indirect irradiance is much more expensive to compute than other types of reflection, such as specular rays that do not create multiple branches in the ray tree.

Best,
-Greg

> From: Jia Hu <hujia06 at gmail.com>
> Date: August 31, 2010 7:01:25 AM PDT
> 
> Hello Greg:
>  
> The speed is pretty fast. But I found there was a 10% difference sometimes even if I use the following command (ab=8 and ad = 4096). Should I further decrease lw to reduce the variance between each run?
>  
> rtrace -w -h -I -ab 8 -n 4  -ad 4096 -as 0 -aa 0 -lw 1e-5 -lr -10 -u+ office.oct < points.inp 
>  
> Thanks,
> Jia

---------
> From: Jia Hu <hujia06 at gmail.com>
> Date: August 30, 2010 10:42:45 PM PDT
> 
> Hello:
>  
> Radiance works by calculating three parts, direct, specular and indirect. ab determines the number of ambient bounces (indirect part). But ab has a similar meaning with "lr". What is the difference between them?  Is that right lr (positive) should be larger than ab?
>  
> As always, thank you,
> Jia