Black Reflections in Complex Glass

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Sharlybg
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Black Reflections in Complex Glass

Post by Sharlybg » Fri Feb 07, 2020 11:06 am

I'm struggling to get correct SDS reflection on a complex Glass rendering !

Caustic cache is slow and can't catch thoses sds reflection. Bidir also can't . So i wonder if BIDIRVM can do something ? and how to expose it ?
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Sharlybg
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Re: Black Reflections in Complex Glass

Post by Sharlybg » Fri Feb 07, 2020 11:22 am

Here is the render vs real image i want to match :
test sc.jpg
As you can see there are lot of black reflection on the lux one.
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B.Y.O.B.
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Re: Black Reflections in Complex Glass

Post by B.Y.O.B. » Fri Feb 07, 2020 12:59 pm

It would be good to have the scene.
In general, what you see in glass is the environment - maybe the surroundings just contain these dark areas? How does the environment look like?
I guess you have already made sure that the specular depth is high enough?

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Dade
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Re: Black Reflections in Complex Glass

Post by Dade » Fri Feb 07, 2020 1:00 pm

Sharlybg wrote:
Fri Feb 07, 2020 11:22 am
As you can see there are lot of black reflection on the lux one.
I doubt it is SDS related because the scene looks like pure specular bounces to me (it is hard to say without a more general view of the scene). Have you tried to use some really looooooong path depth ?
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Sharlybg
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Re: Black Reflections in Complex Glass

Post by Sharlybg » Fri Feb 07, 2020 2:12 pm

You are right. i get closer. but really still miss lot of internal reflection compared to real photo.
sc.jpg
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Re: Black Reflections in Complex Glass

Post by B.Y.O.B. » Fri Feb 07, 2020 2:15 pm

The real glass probably has a lot of tiny surface imperfections, like small scratches, bumps, dust particles, grease etc. that all catch the light a bit.

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lacilaci
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Re: Black Reflections in Complex Glass

Post by lacilaci » Fri Feb 07, 2020 3:24 pm

not sure if applicable to luxcore but good results...
https://www.youtube.com/watch?v=Sv2wqwsvx-8

kintuX
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Re: Black Reflections in Complex Glass

Post by kintuX » Fri Feb 07, 2020 3:36 pm

... and as noted many, too many times already, LuxCore Glass surface can't do it (multiscattering)!
For an example, make it fully rough and watch it go over to the dark side. Even utilizing WHITE Shadow Color. :twisted:
BadGlass_by_LuxCore.jpg

A way to hack it - mix, add Arch. Glass to it (the middle one on image below)
NOTE: from the days before Shadow Color option on materials was introduced, tho only for OCL

Image

tho I'm not sure how it works now, haven't tested since

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Re: Black Reflections in Complex Glass

Post by lighting_freak » Fri Feb 07, 2020 5:30 pm

Hi
Sharlybg wrote:
Fri Feb 07, 2020 2:12 pm
You are right. i get closer. but really still miss lot of internal reflection compared to real photo.

sc.jpg
What did you change to reach this improved result.
What's the exact set up? Is it a glass cylinder with an air helix inside? What do you use as environment lighting?

Where is your reference from?
Thanks for helping to understand the behaviour.

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Sharlybg
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Re: Black Reflections in Complex Glass

Post by Sharlybg » Sat Feb 08, 2020 9:01 pm

What did you change to reach this improved result.
What's the exact set up? Is it a glass cylinder with an air helix inside? What do you use as environment lighting?
Hi sorry for the late reply. i 've just added a 1/2 sphere dome with some point light shining under it to simulate a brighter env.
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