1. When rendering to Mplay and then save frame into disk, houdini won't write out the correct Cryptomatte metadata, neither Houdini COP or Nuke can use those Cryptomatte.
2. Cryptomatte aov set by different methods seems to write non-generic metadata.
- the first way is set the Cryptomatte aov on the karma render settings node, set the extra render vars 'CryptoObject'. it will give the 'CryptoObject' aov, and it can give the correct metadata that Houdini and Nuke can read.
- the other way is set the Cryptomatte aov on the 'Karma Cryptomatte' node (will output CryptoPrimitives aov),if use this method only Houdini COP can read the metadata and use the Cryptomatte correctly. (Nuke can't even read beauty pass when there is 'CryptoPrimitives')
3. when using 'CryptoObject' method , if read the EXR file in the COP and use AIdenoiser to denoising the image, and use COPROP render it out, the metadata will also mess up (can't use Cryptomatte after denoising and render it out).
The above three problems, I think there may be some Nuke side issues? But the use of aidenoise in cop will break the use of Cryptomatte, it seems that it should not appear.
I have attached the exr file rendered by both methods: https://mega.nz/folder/PkR1XDzb#b_CVkNNoLodQZh858DFjig [mega.nz]