Chaos Corona for 3ds Max > [Max] General Discussion

Cryptomatte + Nuke, what's the ideal workflow?

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moriah:
Hi,
I'm a long time Vray user, and i'll have to use Corona for an upcoming automotive animation project. From what i've been testing, cryptomatte is implemented differently in Corona than in Vray.

Vray: Add your Cryptomatte render elements » save multipart exr with dwab compression » load a single exr in nuke (or with separate cryptomatte in recent vray versions)
Corona:
A. Add your Cryptomatte render elements » save cxr » it's not a multipart so every render element is split which is awful » rename cryptomatte cxr to exr » beauty cxr in nuke doesn't have any color corrections saved, but cryptomatte is loaded.
B. Render your beauty with standard render elements with multipart exr » calculate cryptomatte separately in cxr » rename to exr » load in nuke.

With A we lose the multipart exr and there's manual renaming of cxr, also the beauty is unusable directly because it lacks the color corrections in vfb.
with B we have to calculate everything twice which isn't the ideal workflow either.

My question is if i'm missing something? We use deadline and renderstacks for the shot prep and management. Cryptomatte is a MUST for compositing, so what's the best workflow here?

Thank you,

RecentSpacesSam:
Something I've done before is to use Gaffer to resplit/recompress the cxr into multi part, it is a bit slow but if you can implement it into your deadline workflow then that's not really an issue.

TomG:
Also, shouldn't have to calculate everything twice I believe - you could just render with ALL elements (including the cryptomatte), save to CXR and rename to EXR to load the Cryptomatte and any elements other than the tone mapped Beauty, and then without re-rendering save just the tone mapped beauty to EXR or other high bit depth format. So rendering once is all that's required, "just" saving twice.

As a note, CXR not containing a tone mapped Beauty is already slated to be changed, because we'll need that to work with the AI Enhancer, so in a future update it will remove the need to save twice.

Since I don't use Nuke, can you clarify on "it's not multipart" as to what that means? Someone who does have Nuke had a look at EXR from V-Ray and "EXR renamed from CXR" from Corona, and the cryptomatte worked identically in each (you see the cryptomatte image, and can just click on the item you want to mask by to have that activated). Thanks!

moriah:

--- Quote from: RecentSpacesSam on 2025-03-07, 13:54:44 ---Something I've done before is to use Gaffer to resplit/recompress the cxr into multi part, it is a bit slow but if you can implement it into your deadline workflow then that's not really an issue.

--- End quote ---

Appreciate the tip, however i think i still have the problem with the beauty not being tonemapped correctly in CXR

moriah:

--- Quote from: TomG on 2025-03-07, 14:06:26 ---Also, shouldn't have to calculate everything twice I believe - you could just render with ALL elements (including the cryptomatte), save to CXR and rename to EXR to load the Cryptomatte and any elements other than the tone mapped Beauty, and then without re-rendering save just the tone mapped beauty to EXR or other high bit depth format. So rendering once is all that's required, "just" saving twice.

As a note, CXR not containing a tone mapped Beauty is already slated to be changed, because we'll need that to work with the AI Enhancer, so in a future update it will remove the need to save twice.

Since I don't use Nuke, can you clarify on "it's not multipart" as to what that means? Someone who does have Nuke had a look at EXR from V-Ray and "EXR renamed from CXR" from Corona, and the cryptomatte worked identically in each (you see the cryptomatte image, and can just click on the item you want to mask by to have that activated). Thanks!

--- End quote ---

Thanks for the clarification. I'm not talking about single images, but rather several animations being saved via deadline. I don't think there's an option either in Renderstacks or Deadline to double save the same file with different options after being rendered once.

When i mean multipart, it's 1 exr with all the passes inside. Right now CXR has everything split, each render element is a separate file. Maybe i'm missing an option to make it multi part like EXR?

If CXR had the tone mapped beauty we had our problem solved i think. Any ETA on that option?

Appreciate the help!

edit: Actually Renderstacks only supports corona exr saving, no cxr at all.

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