[Radiance-general] rtcontrib parameter settings

[Andy Stone]

Hi all,

I've been using rtcontrib recently and I'm having problems finding a set
of rendering parameters (ad and lw) that don't give "out of memory"
errors but do give sufficiently accurate results.

About the highest settings that I can use before an out of memory error
occurs is:
 
cat luxmeters_test_office.txt | rtcontrib -V+ -o solar_coefficients.bin
-M sun_modifiers.txt -fad -ab 5 -ad 4096 -lw 1e-8 -I+ -h
octrees/scene_with_suns.oct

...but when I use these settings the results contain a lot of noise.

The scene consists of a fairly complex building and 72 light sources
(representative suns for the year), each of which has a unique modifier
so that I get a coefficient for each light source at each measurement
point.  

So far I've come up with two possible explanations for my problems:

1. I'm getting my settings all wrong.  I'm using -ad and -lw to control
the accuracy, but I haven't got a good feel for how to vary them -
should I set -ad as I would for a normal rtrace-type calculation and
then reduce lw until I get what I want, or does ad need to be higher for
an rtcontrib type calculation?  Or is there another setting I need to
look at?

2. I'm using cygwin.  Is anyone aware of any memory limitations with
cygwin? I've seen the web page about increasing the memory available to
cygwin (http://www.cygwin.com/cygwin-ug-net/setup-maxmem.html) and that
didn't help at all - apparently cygwin on my machine has a maximum heap
size of about 1.5Gb.  

Does anyone have any suggestions?

Thanks,

Andy Stone