close up glass = noise

[AdrienG]

Hii
I ve got to do a very close up shot with a very thick glass and guess what : noise
I ve tried to play and match settings from different posts but it seems that there is no clear way to speed up rendering.
When you look at the first image with the glass activated, it looks like there s a halo on the green/white. I cant figured out where that come from, no roughness on the glass shader and no post effects. it could be a clue to figured out the noise.
My lighting : octane plane light with a gobo texture. Before that i had an hdri. With/without textures, that doesnt seem to change anything for render times.
I d like to keep caustics with PT kernel.
Also, the glass mesh has the exact same topology on the front and back, so no weird distortion. Perfect normals.
I use a lot redshift but i wanted to again give a try with octane for a better realistic look : it works great on distant shot but here on close up i m a bit stuck. The rendering time could be fatale.
Any clues ?
Cheers

[james_conkle]

Solving caustics is fairly expensive but there’s a few things you can do to speed up render time without using fake shadows.

Maybe a combination of the following will help:
-Use AI lighting mode with the primitive light models (won’t see benefits with geo that’s emissive / only primitive/spectron lights )
-Decrease the hotpixel removal from 1>0.7-0.8
-Decrease GI clamp to <500
-Increase caustic blur as high as you can while still seeing the caustic effect.
-Decrease specular and glossy bounces as much as possible
-Increase parallel and max tile samples as high as possible (limit will be the sliders or VRAM)
- turn on adaptive sampling and increase the threshold while still being acceptable.

[AdrienG]

thanks for the tips. I tried and didnt found a magic wand to get the noise down with a fair amount of render time. I guess it s just the way octane is built.
Isn't there a possibility that a medium on this thick glass would help the calculations ?

[elsksa]

I d like to keep caustics with PT kernel.

While updating/upgrading during a project is not recommended, there are ways to have various renderers or versions in parallel, or perhaps, this project could be fully backed-up and tested on a 2022+ build with the Photon Tracing Kernel? It's truly a new stellar kernel for caustics.

Otherwise, if everything that james_conkle mentioned has been carefully verified, I would consider denoising individual AOVs in post.

[AdrienG]

Thanks for the advice and underlining the new 2022+ photon tracing kernel
I'm tryin that very soon on M1 and put a feedback here.
Another question, would it be interesting to low res and blur the hdri (environment) and specify in the visible environment the original one (6k) ?
I remember that this blur hdri thing would help for noise in previous/other renderers at the cost of a blurrier/not as sharp lighting/shadowing.

[elsksa]

Thanks for the advice and underlining the new 2022+ photon tracing kernel
I'm tryin that very soon on M1 and put a feedback here.

I didn't know you were on MacOS (or didn't pay attention to it). Good to know.

Another question, would it be interesting to low res and blur the hdri (environment) and specify in the visible environment the original one (6k) ?
I remember that this blur hdri thing would help for noise in previous/other renderers at the cost of a blurrier/not as sharp lighting/shadowing.

I would always favor having as the primary lighting, native renderer's "area lights". HDRI have their place in some cases. Using native lights will always be advantageous and provide highest amount of creative and technical (sampling included) control. Especially in product visualization.

[AdrienG]

Actually, i m on win and macOS(for testing) but i found out that the 2022 RC1 exists for maya/win; didnt see that

So i tried a basic scene on my win/maya2022/2022RC1/1080ti config
The photon tracing straight out of the box doesnt bring any speed :

[elsksa]

The photon tracing straight out of the box doesnt bring any speed :

It doesn't until the concerned materials have "Allow Caustics" checked (it's a checkbox).

I've wrote a whole guide on Octane Caustics, from PT, PMC to the latest Photon Tracing kernel. Let us know how it goes.

Edit: I just updated the page with slightly additional information and clarification.

[AdrienG]

great thanks ! i gave a try on the standalone 2022RC1 : that s awesome, the speed for rendering caustic is phenomenal... !
I ll dive into the guide asap.
Tho, there's a little issue : no checkbox for "allow caustics" in the maya plugin... (it s a specular mat)
any clue ?

[BK]

great thanks ! i gave a try on the standalone 2022RC1 : that s awesome, the speed for rendering caustic is phenomenal... !
I ll dive into the guide asap.
Tho, there's a little issue : no checkbox for "allow caustics" in the maya plugin... (it s a specular mat)
any clue ?

Hi AdrienG,

Thank you again for reporting this issue.
We have requested our dev to implement "allow caustic" checkbox in the future release!

cheers