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Amir Kadiev avatar image
Amir Kadiev asked

Is the Optix denoiser in Arnold 7 worse?

When I updated to Arnold 7 and rendered an image I had previously with Arnold 6.2.1.1, using the GPU and Optix denoiser, I noticed the image looked blurrier. I hadn't changed the settings so are there any that I have to now that I've upgraded to 7? Since then I've downgraded back to make sure and it (at least to me) looks sharper.

I've uploaded the images (at different resolutions) to compare.

I've also uploaded the 2 renders in video format.

(I'm using Maya 2020.4 and NVIDIA GeForce RTX 2080 version 472.12 (Studio Driver)).

gpudenoiseroptix
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I've uploaded a gif/mp4 in case the differences aren't clear enough: https://i.imgur.com/RLSrCdM.mp4

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I think the only change we made was to add specular reflections and refractions for denoising. This should have made it look sharper, not blurrier. Or more specifically, it should look more accurate.

Can you post an Arnold 7 image showing what it looks like if you turn off denoising but use the same number of samples? Also, can you post another image without denoising but this time with enough samples that it is converged? To speed things along, feel free to render just a sub-region that shows lots of the blurring.

It might be interesting to also try the imager_denoiser_oidn that is in arnold 7.

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Sure, I've uploaded the images to imgur.

I'm not sure what you mean by "enough samples that it is converged".

Also are the hyperlinks not working in my original post? I can't seem to open the Imgur and YouTube links on my end.

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Yeah, those links seem to be empty. Can you directly paste the URL instead?


As for converged, I mean increase the AA until you get a mostly noise-free render without the help of denoising. This will give us a correct reference image to go off of.

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Thiago Ize avatar image
Thiago Ize answered

Thanks for providing the scene. Looking at the denoise_albedo which is used in Arnold 6:

denoise-albedo.jpg

and denoise_albedo_noisy from Arnold 7:

denoise-albedo-noisy.jpg

I think makes it clear what is going on. The 6 is missing albedo information in the mirror part, so it's black, and this combination of black mirror face and the grey mirror edges work out in your favor and the optix denoiser is able to detect that these edges are important and shouldn't be blurred.

The 7 albedo happens to have the mirror face and the mirror edges almost the same color (it's using the base and specular colors you assigned to these shaders), so the optix denoiser has a hard time telling them apart and thinks this is all a single feature and blurs it all together.

While this might be an unfortunate regression for your discoball scene, scenes that are mixing different materials (more specifically materials with different albedos) normally see an improvement. A great example is at https://docs.arnoldrenderer.com/display/A5ARP/7.0.0.0 where the sima model has blurry hair with Arnold 6 optix denoising and really nicely denoised hair with Arnold 7 optix denoising (scroll down to the "Higher quality AI denoising" section). There are other good examples when specular shaders and diffuse shaders are mixed together, such as a metal stove next to a wood table...


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So for this one instance, 6 happens to work in my favor.

Thank you for taking the time to answer this.

I guess I'll just stick to 6 for now.

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