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Messages - noldo

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General Discussion / Re: Tonemapping - Plz Halp
« on: 2020-05-03, 07:56:58 »
Since I never tested fstorm I cant tell what causes this but I noriced this on Bertrands scene he sell. The Fstorm has much stronger direct light. Why is it? Clamped GI? Is it accidental or intentional. It gives the space more readable light in way that I doubt is due to tonemapping.

Someone would have to do a deep dive becayse the features have odd parity in behavior. Fstorm HDRI has two modes (weird option to cut off direct light?), their portal light effectively becomes new area light (like one option in Vray).

Very hard to pick out what exactly is the cause with so many variables.

With Dubcat, we suspected the shader. I wonder if something lije OrenNayar wouldnt cause more highlights from durect light?

I was trying to pinpoint what is the difference between the two engines and came to the same conclusion as you have Juraj that in Fstorm light seems to be more directional.

Flash-light renders looked totaly photorealistic back in the vray 3 days even with crappy shaders. This thogether with superior tonemapping is imho the key to ultimate realism.

Can't say tho whether the directionality comes from the shader as you guys with Dubcat suspected or form the GI algorithm.

Asked about Oren-nayar shader model in the daily builds but the devs haven't picked up the conversation. Take a look:



It instantly looks 10 times more realistic. The devs tho are busy with according to trello "key new features" like faster colour picker....

Absolutely, but fstorm also manages the diffuse roughness better, with much softer brightness variations as the roughness increases

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Work in Progress/Tests / Re: dubcats secret little hideout
« on: 2019-02-02, 10:20:48 »
Hi Dubcat!
I am an octane render user, but this post is very interesting!!!
I think your "Specular To Ior v.2" LUT is a bit broken (sorry for my english)
If i convert a sRGB 59 grayscale image (1.5 IOR), the lut give me a value of 167.
I think the correct value is 170 (1/IOR = 1/1.5 = 0.6666666666 => 0.666666666x255=170).
Seems your LUT multiply the value x 250 instead of 255.
Thanks for your work!

P.s. Maybe my fault, wrong monitor color profile?

P.p.s. After some more investigation, i found a way to convert specular to IOR map in octane, but i think corona treat the IOR map the same way (a grayscale value that represent 1/IOR value)
I connected in nuke an expressioni to the specular map with the following formula "1/((r+2*sqrt(r)+1)/(1-r))", then connect the output to a writer image.

P.p.p.s. Your LUT is correct, my fault, i don't understand why 167 instead 170... Bah!

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