My first post here , i've been following luxrender for about 6 months :downloading builds looking at forums etc.. and this is my first test image .
I'm very fascinated by the Luxrender project .. it's an unique blend of very ambitious technical targets (spectral render ? how sci-fi is that !) and yet, there's a great attention to practical aspects : gui , usability . This combination really impressed me.
Not easy to get started though, Lux is mainly an unbiased physically accurate render .. for overnight renders is easy to setup ... but what about keeping the advantages of a physical based
engine and sacrifice the physical exactness
to favor speed ? it sure requires knowledge and study , but I'm starting to be very optimistic about that
This picture was rendered with hilbert / distributed path .
on a q6600 4gb ram ,ubuntu, Lux rc4 64bit. 1600x1200 pixels , The hilbert bucket cycle took 20min (8spp) then i stopped after 1h20min at 24spp. Bloom and glare in luxgui .
No particular story : just an interior test room, 200k quads , statues from Stanford scans and the3dstudio.com
here are some considerations, let me know what you think ...(and correct me if i'm wrong!)
- high number of glossy samples : that made a real difference in speed !
glossy reflections require much more rays and samples to converge (than diffuse) so : 1 glossy / 1diffuse samples means that, by the time you have 10 glossy samples, the image is still noisy because 10 samples for glossy isn't enough ..but you're wasting samples on diffuse rays that are already noiseless.
i used 1 diffuse / 4 glossy samples . Rendertime was 1/3 of using 1 glossy / 1 diffuse.
- samples per pixel for a clean image : depend a lot on the sampler and integrator :
Metropolis might be still noisy at 500spp , lowdiscrepancy + bidir converges at about 100-200spp .
This pic used hilbert / distributed path : with 8spp was decent (!) and almost noiseless at 24spp.
-sunsky is soo slow : not just in lux , it's a nasty light type : a huge arealight going thru relatively small openings ..
and it's supposed to light the room evenly (=lots of bounces + the ones needed to reach the room )
Not to be underestimated : unless the engine is heavily biased and interpolates samples .. sunsky in interiors requires a lot of samples.
In this pic i used arealights on windows with a gradient (brown to blue ) ..cheap trick i know, but it's another 2x speed gain.
Maybe a sample multiplier per lightgroup (not possible yet , right?) so to calc. 2x samples for sky and 1x for artificial lights ..could be fast and more accurate.
Thanks for viewing and for any comment, i'll post more versions with other setups.
EDIT: here is a pic of the setup :
note the the number of bounces is very low , just the bare minimum .
i highlighted with a yellow box the parameters i understand (more or less
) and tweaked with a reason , the rest is from preset or random testing .
(there isn't much documentation on those but i guess it's because lux is in costant developement , and those might change)
Bounces and samples depend -of course- on the specific scene ..i'd say mostly on the amount of direct / indirect light .
EDIT2: in further tests i reverted the settings outside the yellow box to the presets, ignore those in the pic (or, suggest me how to use them