Trouble with glass reflections

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Asticles
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Trouble with glass reflections

Post by Asticles » Wed Sep 16, 2020 9:31 pm

Hi all,

I'm having some trouble with glass reflections, after more than 7000 samples, I'm getting few samples on a glass reflection, compared with the rest of the space. What also makes the denoiser fails in that area. (Glass of the left side of the attached image).
7299samples.jpg
Have tried with metropolis and sobol, and I'm rendering on cpu.

Any hint what could be the solution?

Thanks.

zeealpal
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Re: Trouble with glass reflections

Post by zeealpal » Wed Sep 16, 2020 10:24 pm

Nota solution to the noise, but have you tried using OIDN via the compositor instead? I can't find it at the moment, but I remember a video that denoised the passes individually and combined them, and it did work better for something I rendered.

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Dade
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Re: Trouble with glass reflections

Post by Dade » Wed Sep 16, 2020 10:25 pm

Are all light sources outside the box enclosed by the glass ?
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Asticles
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Re: Trouble with glass reflections

Post by Asticles » Thu Sep 17, 2020 7:11 am

Thanks for the response,

Dade:
yes, all lights are outside the glass.

Zeealpal:
I will try, but still there is much less sampling in the glass reflection.

Regards.

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Sharlybg
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Re: Trouble with glass reflections

Post by Sharlybg » Thu Sep 17, 2020 8:56 am

Your scene is a nice challenge. Rendered on CPU high resolution with some reflective and specular surface plus small artificial light in an enclosed space.

This is my result on a old i7 4930k. without denoiser in 5mn :


Raw
Bath test.jpg
Denoised Edit 15mn
Bath test denoise.jpg

Settings

Clamping = 20

Light tracing = on

PGI = brute force radius scale (1) Photon count (2)
Caustic cahe = Default
DLSC = default

Meshlight with simple plane (no circle) importance set to 20.

Glass shadow color = 75% white
Last edited by Sharlybg on Thu Sep 17, 2020 9:18 am, edited 1 time in total.
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Asticles
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Re: Trouble with glass reflections

Post by Asticles » Thu Sep 17, 2020 9:17 am

Nice!

Try to remove the lights from inside the shower and change the outer ones with ies lights, not mesh. Maybe this is the problem.

Edit, when using PhotonGicache, the difference is much more noticeable.

Regards

Asticles
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Re: Trouble with glass reflections

Post by Asticles » Thu Sep 17, 2020 9:44 am

hmm, raising the importance of the ceiling lights seems to have solved a lot the situation. Still making tests.

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Dade
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Re: Trouble with glass reflections

Post by Dade » Thu Sep 17, 2020 11:21 am

Asticles wrote:
Thu Sep 17, 2020 9:17 am
Try to remove the lights from inside the shower and change the outer ones with ies lights, not mesh. Maybe this is the problem.
Yes, all the surfaces inside the box closed by the glass are SDS paths. There two options:

- use PhotonGI caustic cache with periodic updates and have long rendering times;

- or use Hybrid glass (aka set glass shadow transparency so light can go directly trough it) and have very fast rendering at the cost of less realism.

Or have a mix of both like suggested by Sharlybg.
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Asticles
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Re: Trouble with glass reflections

Post by Asticles » Thu Sep 17, 2020 11:43 am

Actually, it is hybrid glass.

Can you explain me that Photongi settings?
Periodic updates are enabled by default.

Thanks

Asticles
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Re: Trouble with glass reflections

Post by Asticles » Thu Sep 17, 2020 11:48 am

Wow, samples/sec dropped A LOT.

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