Unexpected channels appear in crypto-related render passes

[huseila]

Hi, I noticed that some potentially redundant channels are being generated when integrating crypto-related passes like crypto_asset, crypto_object, and crypto_material into a merged EXR with other AOVs (please refer to the attachment). I'm wondering why these extra float-type channels are generated and whether they carry any useful information for compositing. If these channels are indeed redundant, is there a way to remove them in Katana?

 

 

[Stephen.Blair]

Those are the actual Cryptomatte AOVs. Remove them, and you won't have any Cryptomatte mattes.

[huseila]

Hi Stephen,

I'm still a bit confused. Since the cryptomatte data is already stored in channels without number suffixes (such as "crypto_asset_crypto_asset", "crypto_material_crypto_material", and "crypto_object_crypto_object" - though I'm not sure why the names are duplicated), why can't we remove the channels with number suffixes? I assume these float-type channels are likely intermediate products used to generate RGBA Cryptomatte AOVs and should be discarded after the process. Is my assumption correct?

[Stephen.Blair · Accepted solution]

No, those are required. See the Cryptomatte Specification here: Cryptomatte/specification/cryptomatte_specification.pdf at master · Psyop/Cryptomatte · GitHub

Those channels are for the "depth": how many objects can exist at the same pixel, and what is their order

[huseila]

Thanks for the document - it cleared up a lot of my confusion.