cryptomatte with dwa compression

Derek Flood

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Sep 20, 2017, 8:19:07 PM9/20/17

to alshaders

It appears that Cryptomatte is not working with a render saved with dwa compression (both dwaa and dwab). That is I cannot pick the mask in Nuke. If the file is rendered with zip compression it works fine.

Is this a known issue?

I'm guessing it has to do with how the crypotomatte aovs are being compressed by dwa. I suspect it is getting lossy compression which is then messing up the mattes.

Note that the test I did was for Arnold 4 using the ALsurface shader in Maya. I have not tested this in Arnold 5.

Anders Langlands

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Sep 20, 2017, 8:34:45 PM9/20/17

to Derek Flood, alshaders

Yeah DWA is lossy. The mattes are hashes encoded as colours so anything which changes the colour values even slightly is going to break it.

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Derek Flood

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Sep 20, 2017, 11:12:23 PM9/20/17

to alshaders

That's a pity. Is there a way to make DWA use RLE or ZIP compression on the cryptomatte AOVs instead? Maybe Jonah has some ideas? (...mentally summoning Jonah...)

Anders Langlands

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Sep 20, 2017, 11:26:43 PM9/20/17

to Derek Flood, alshaders

Pretty sure you can't mix compression within the same file. If you split the cryptomatte AOVs out to a different file you could change the compression type just for that file.

Anders Langlands

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Sep 20, 2017, 11:48:14 PM9/20/17

to Derek Flood, alshaders

I stand corrected, DWA has some hard-coded magic constants to recognise channels that it thinks are worthy of losless compression. I'm not sure if there's a way with the current build to change the channel names that Cryptomatte outputs to play nice with DWA.