Option For Making Only One Render Element Multichannel EXR

[paross20]

Hello,

My workflow deals with single frames going from Maya to Photoshop, so I split all my render elements into separate .exr files. From what I can tell, the way to do this is to choose 'exr' as my Image Format, as opposed to 'exr (multichannel)'. This works great,
however I noticed for the 'Cryptomatte' Render Element, it does not split each layer into a separate exr file properly. In other words, if I choose 'exr (multichannel)', when I open that up in Photoshop, I see a lot of layers for cryptomatte (around 13), but if
I choose 'exr' as my Image Format, I only get three cryptomatte .exr files saved out separately instead of the 13 I expected.

Is there a way to have only the Cryptomatte Render Element be multichannel or is there a setting I'm missing? Ideally I would not have to render twice on two different render layers.

Cheers,
Patrick

[hermit.crab]

Yes, those additional 10 are the maks for each object in the scene (mattes are extracted). I think Cryptomattes are meant to be used through multi-channel files to work properly (correct me if I'm wrong). Is there a particular reason to avoid multi-channel files except for, perhaps, filesize?

[paross20]

Hello!

Thanks for your reply. Yes, so the reason to have the "Back to Beauty" Render Elements be separate .exr files is to support a non-destructive workflow in Photoshop. If each render element that makes up the beauty is a separate file, we can do a 'Place Linked..' operation in photoshop, add those together, and save the document as a .PSD. Then the artist can do work on those layers (create masks or adjustment layers) and if the render gets updated, we can then re-link those base layers to a new render while preserving any work around it the artist may have done. If you do a 'Place Linked..' operation on a multi-channel exr, it will link in the file, but it will appear as only the beauty layer. Then to have access to all the render elements, you have to double click into that layer, which then essentially opens up that multi-channel exr. If you do any edits at this level, you have to save over that multi-channel exr, which then breaks the non-destructive workflow.

Yes, it appears to have proper access to all the mattes the Crypto Render Element needs to be multi-channel. I've used Arnold and Redshift using this workflow, and both of those render engines preserve the multi-channel aspect of the crypto render element, whether or not you choose to merge your elements into one exr or not. I think this makes the most sense and maybe the less disruptive route to implement into VRay. Curious to get feedback if I'm crazy or if anyone agrees?

Best,
Patrick

[hermit.crab]

Thanks for the detailed feedback. I did some testing with Arnold and, indeed, Cryptomattes are saved as a separate multi-channeled file (and it does make sense for it to function like this). I've logged an improvement request (internal bug-tracker id: VMAYA-10989) for this functionality to be implemented in V-Ray as well.

[paross20]

No problem, thank you for taking the time to look into it as well! Awesome, thank you very much!!!

All the best,
Patrick

[paross20]

From your experience, how long would you guess before this finds its way into a release?

[hermit.crab]

I cannot say, really. Usually, priority is determined by the number of requests, so it depends.

[SonyBoy]

I'm sure I'm stating the obvious, but a simple workaround for this in the meantime would be to render out multichannel EXRs and then simply break that out into separate channels before bringing things into Photoshop. Either Nuke or After Effects could do this easily. It's an extra step of course, but once you have a template built would take seconds.