Light Simulation

[zouhair_psi]

hi, realy nice render , i like the small tree render.

by what soft you did the modeling of the tree?

[Coronaut]

This is what i am talking about.
Size was changed but intensity wasn't.
Well size isn't that much changed as "semi-soft" portion is letting lets poke shit in woods and say 30% of sun rays(hard light) is missing all water, dust etc. in cloud and rest of 70%(sun rays) is diffused as photons are diffracted trough vapor(water in cloud) and turned away in some other direction. I am just saying all this is way too much over the top. Sun size does change difference of how much rays there are, but this is special situation as(refer to attachment) Hard light portion of the sun is lets say 20-25% and instead of doing 1300w or whatever lux per square meter it does 20-25% of that, and that is something i believe you can't measure but i am sure someone is simulating something like that... anyhow over the top :)
Tree is modeled in max(nothing fancy) done those small branches in Zbrush.

[Coronaut]

Hour and 22 minutes 800passes sample 8, dof hasn't improved dramatically, i think it would be better if i was to leave it longer. But anyhow. Next time.
...those stupid stomps on leafs... what i was thinking :D

[Ludvik Koutny]

If there is noise in direct lighting, rather than indirect, you can leave GI/AA balance down at 8, as it will really help DoF, even though it may not  seem so, and crank up Light Samples multiplier instead. That's what mostly takes care about noise from direct lighting. Environment light is considered to be direct light too, by the way ;)

[Coronaut]

This will be last contribution to this topic.
Here is one on first look very simple scene... but in fact it is very demanding as it have 3 sheets of glass, DOF, bunch of glossy reflection, dome(HDRI) lights, and it's very very low light.
Original photo was taken with canon5d, sigma 1.4@1.4 Iso 1600 shutter 1/100, it was sunset with intricate lighting(dark clouds with orange highlights(very bright spots) and unfortunately i wasn't able to reproduce similar highlights on chrome and aluminum parts as i didn't have that kind of HDRI...
Anyhow... I didn't like how dof cuts out it seems to me like depth falloff doesn't have right curve... Glass transparency is pretty much as it should be and it doesn't kill high lights like in Vray.
p.s. what test would this be if i wouldnt be able to fuck up... this aluminum rail is different as i was too lazy to measure it on the window i did take picture instead i did on the one above my head and it has slightly different one...

[Coronaut]

Vray versions. As i did mention in vray versions there is clear absence in highlights inside that metal frame of the glass... Also i had to remove glass out of GI as it was too dark... and cuz i want to replicate real world condition not fake(vray always had this problem with glass absorbing too much rays)
I didn't have this absorption problem with vrayRT but i did have(unsupported material and all that scheisse...)
Render times
Corona 8:30(hours) 422passes i think its too long as it was done on 28threads in DR mode but i didn't check thin glass(on purpose) 8pt samples...
Vray 3:20(hours) Pretty high settings(except leaving glass out of GI solution) i left caustics and all that stuff.
Vray_RT 30minutes(resolution almost 50% lower) Two GTX780 cards
Arion(i should spend that money on drugs when i was in Amsterdam few months ago)... Disappointment, i am sorry for lost time when i was converting scene... It just couldn't done anything...
I will try 100 passes with corona just to check if i can get faster times.
That is about it. From this different scenarios.
Cheers people!

[romullus]

I think that refraction transparency of your glass material is to low. Look how big difference in sky's exposure betwen direct and through glass views if you compare it with photo.

[Coronaut]

Yes, that is what happens when refraction is on, and when you have 2 completely different sky's and 3 layers of glass. But i am sure you didn't wanted to state obvious, so please, tell me if you have any trick down your sleeve, how should i increase transparency of already unrealistically transparent glass? 
Also if you think that this corona version has major discrepancy between glass and air, check out some other rendering systems, and if there isn't any i would love to see some of this kinda tests from you.
Also to take into account how "real" lens doesn't have ideal Optics(why do i write with what lens photo was taken?) but instead has vignetting and bunch of different kind of distortions, not to mention that i have filter mounted on lens... Maybe what you see as brighter sky on render and same brightness on photo is in fact what's wrong. Or maybe something completely different. I get how this is gallery section but in fact this should not be in gallery as maybe there is some people who will look for something that you tend to overlook as it is more subtle than glowing green or blue.
Anyhow, as there is "Thin" option there just so you can get airy, unobstructed GI, why not click it, right?
And as i don't want to be jerk and to be "talking shit and stuff" or give your comment any deeper meaning here is what i am talking about.
http://www.roofingsuperstore.co.uk/browse/pitched-roof-windows/velux-replacement-panes/laminated-8.html  0.78 light transmittance...
http://en.wikipedia.org/wiki/Transmittance <---more on that theme
If you already thinking, please continue to do so.
Cheers.

[Ludvik Koutny]

In Vray, GI is what takes care of caustics, so if you have left the glass out of GI solution, then the comparison is very unfair. So either enable GI for glass, or in Corona, disable Caustics on your glass material ;)

[Coronaut]

Yes, my previous post and render above your comment is same "solution" as in Vray but it is in corona. As you can see it is 3 time faster then Vray.
Anyhow it would be faster even with GI caustic as 100 passes would be done in less then 2 hours.