[Radiance-general] ambient resolution and memory

[Jack de Valpine]

Hi Lars,

Wow, 2 weeks. That seems pretty extreme. What is your scene? Are you 
running on your OpenMosix cluster?

Below are some answers and thoughts....

-Jack

Lars O. Grobe wrote:
> Hi,
>
> I hope these messages will arrive one day when radiance-online.org is 
> back again...
>
> I am getting into trouble with rendering a large detailed model. If I 
> am setting ar as usually (ar=scene boundary/detail dimensions, I get 
> something like -ar 2000. That leads to slow processing with huge 
> memory useage (around 1.6 GB).
>
> I wonder if there is a way to reduce the general resolution in such 
> cases and increase accuracy in detailed regions only by ad, as and aa.
>
> I also wonder if there is at least some performance to win by changing 
> / releasing ambient parameters for high-res pictures after the 
> ouverture produced some values. While people did such things for a 
> while, later posts suggested that this is not safe. Is this true for 
> ALL ambient parameters?
>
Yes, you can do this but NOT for all ambient parameters.  You should be 
able to make some adjustments to  aa, ad and as, for example:

overture calc: -aa .15 -ad 1024 -as 512
image:            -aa .25 -ad 512 -as 256

where ad and as are getting halved and aa increased by some amount.

How many ambient bounces are you using? I think for an interior scene 
with illums at the window openings you should be able to set -ab 1....
> Finally, I am using mkillum to cut one step from the ambient daylight 
> calculation, illums are covering all windows. Does this influence the 
> simple formula used to calculate ar, or is ar only determined by scene 
> geometry?
>
> I am a bit desperate, as the ambient paramters needed to produce clean 
> images lead to rendering times about two weeks per 1200x1200 picture 
> at the moment here, on a 3.2GHz P4... so I hope to optimize a bit by 
> tweaking ambient calculation. I am already using mkillum and ambient 
> exclude lists to accelerate things a bit. The scene will become even 
> "worse" when I switch on my artificial light sources...
>
It may be worth it (at 2 weeks running time) to do some pretty serious 
experiments with ambient parameters. You might also want to consider if 
there is geometry that could be excluded from the ambient calculation 
(-ae or -aE), some examples might be very small geometry and/or geometry 
that has very dark materials applied. Lastly, if you have not even got 
your artifical lights on then you might want to consider if some of 
these could be managed with a glow material with a radius of influence 
instead of illum/light. Also worth considering is whether there are any 
optimizations that you might be able to do to the scene geometry...

-- 
# Jack de Valpine
# president
#
# visarc incorporated
# http://www.visarc.com
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