Problem with Stand Alone Denoiser and Multichannel EXRs/Cryptomatte

[MattClark]

I could be missing something obvious here, but let me explain the issue:

I've been rendering out some sequences as multichannel exrs, with all my elements, including denoiser and cryptomattes.

I can bring these into After Effects and everything behaves, using the ProEXR2 plugin to split the channels back out, and cryptomattes work as expected with the ProEXR2 plugin.

However, if I run the sequence through the stand alone denoiser (using the version which ships with Vray next) and use it to denoise the beauty and all the elements then the cryptomattes in the resulting exrs no longer work. If I visualise them in AE they look either blank or corrupted.
I've tried excluding them in the 'Select denoise Elements' tab of Vdenoise, but no joy.

Am I doing something wrong? Is this a limitation?

Thanks

[hermit.crab]

Can't seem to replicate the issue, I am able to denoise such an image without any issues. Does it happen with any EXR with cryptomattes? Which version of V-Ray are you using? Maybe share an example EXR prior to denoising so we test it out?

[MattClark]

Just to be clear, the passes to make up the beauty all denoise fine, and add up correctly, but the cryptomattes seem to have missing or incorrect data.

I can't share the production work I'm on, but I just made a test scene and it seens to exhibit the same problem, I'll include the EXR here, before and after denoising.

https://www.dropbox.com/s/54a6pbap49p8glz/EXRs.zip?dl=0

At the moment I'm happy to use the cryptomattes from the original EXRs along with the other elements from the denoised EXRs, I'm just wondering why it happens, whether it's something I'm doing wrong or a limitation/bug?

Thanks

(This is using V-Ray 3.70.01 to render, and the latest stand alone denoiser from Vray Next)

[hermit.crab]

Pardon me, I understand now. Indeed, something may be the matter, I'll talk to our developers about it and report back.

[hermit.crab]

The cryptomattes seem to break only when being denoised themselves, however, this does not seem to be the case for your provided files (they break regardless of being denoised or not). Could you share the scene from which the EXR was exported as well, so we can take a look?

[MattClark]

Yes, that's correct, they break regardless of whether I'm denoising those cryptomatte channels or not. I've included this test scene here:

https://www.dropbox.com/s/w6jfs7oishk7x6e/test.max?dl=0

...although it's worth noting this happens in all my files, perhaps I'm setting them up wrong.

I'm using Max 2015, V-Ray 3.70.01, and the latest Vray Next standalone denoiser.

Thanks.

[hermit.crab]

Thanks for the scene. The issue seems to be V-Ray 3.7 related, however, it seems to be fixed in V-Ray NEXT. Try rendering the provided file with V-Ray NEXT, use the denoiser (without denoising the cryptomattes), load the file in AE and apply the cryptomatte effect.

[MattClark]

Ah, thats a shame, I'm afraid I don't currently own Vray Next. I downloaded it through my account to use the improved stand-alone denoiser, which works without the license.

I guess it's unlikely to get patched for 3.7?

[hermit.crab]

Unfortunately, yes, since there were changes concerning additional metadata being written in the EXRs. For now, you would have to use the cryptomattes from the original EXR as the workaround you suggested.

[MattClark]

Ok, thanks for clarifying.

[isoparmesan]

I'm currently having this same issue with V-Ray Next. It also seems to be creating strange results in my Specular channel, but only for certain materials.

[hermit.crab]

I'm currently having this same issue with V-Ray Next. It also seems to be creating strange results in my Specular channel, but only for certain materials.

Best you send a scene, the exported .exrs, screenshots, and explanation of how to reproduce the issue to support@chaosgroup.com so we can take a look. Mention your 3ds max and V-Ray versions in the e-mail along with a reference link to this thread.