Can't get Cryptomatte to work with Arnold GPU in Max 2026

[AlphaMax9]

Hi, has anyone successfully configured Cryptomatte to work with GPU in Max 2026?

While CPU rendering works fine as usual, GPU rendering produces a red output and doesn't function properly (while it supposed to be supported now, isn't it?). Are there specific settings needed to make the GPU version work? I have everything updated to the latest version as far as I can tell.

CPUGPU

[Stephen.Blair · Accepted solution]

That's just the preview. GPU doesn't output the now deprecated preview.

The Cryptomatte layers are still there and will work in Nuke. Or is that a screenshot from Nuke?

[AlphaMax9]

It's not Nuke - Just Arnold render view (attached). 

In Photoshop, for certain projects, the preview colors can also be useful. So CPU is the way to go for such cases.

Thanks for your reply

[Stephen.Blair]

I do see different RGBA values for the "red" objects, so can you use that?

[AlphaMax9]

Yes! that's a good workaround - as long as we don't have too many objects/materials. While Crypto is not intended to be used like this, it's a quick and effective mask selection in PS.

When it comes to proper layer extraction, I realized I can no longer get it to work in After effects. Regardless of CPU or GPU. Looked up this tutorial, and even author says it’s no longer working since recent updates. Is this a known issue?

https://youtu.be/02my1T_-vyY?si=YER05FfAPbthOvD7&t=210