Cryptomatte Mask no elements available because of object in scene

[Lewis107]

So I was rendering in Max 2021/Vray 5 and noticed that the Cryptomatte wasn't working in the VFB.
The element had rendered but when I wanted to use it as a mask it said - no elements available.
After lots of testing I narrowed it down to a group of instanced objects that were part of another group. The main object was an item I modelled...basically a circle, extruded, with edit poly and just a weighted Chamfer modifier applied.
When I deleted/hid the item the Cryptomatte was available as a mask.

Why would this object prevent this to work normally? It's just it would be annoying if this happens again in a different scene.

Thanks

[yavor.rubenov]

Hello,

That would be strange indeed. What was the objects name ? We've recently found some cases with strange symbols could cause issues. It would be easiest if you could share a scene - you could delete most of the other geometry as long as the issue still reproduces.

Best regards,
Yavor

[Lewis107]

Hello,

That would be strange indeed. What was the objects name ? We've recently found some cases with strange symbols could cause issues. It would be easiest if you could share a scene - you could delete most of the other geometry as long as the issue still reproduces.

Best regards,
Yavor

Yes that was it...for some reason the name of the object was Tilt Table ll=002

Not sure where the II= came from. It should have been just Tilt Table 002 as I never use those symbols when I name objects, so it must of changed at some point.

When I renamed the object the Cryptomatte mask was available again.

Do you want me to still share the scene? What's the best way to do that?

[Lewis107]

Actually I would of named it Tilt Table l 002.....but possibly I added 2 lowercase Ls and the = by accident, not really sure. Unless that's some sort of Max glitch when copying objects or using mirror/symmetry?

Strange how it affects the mask though. I know for next time!

Thanks

[yavor.rubenov]

Indeed the '=' symbol is the problem - internally the Cryptomatte prepares a manifest with all the object names that is saved into the output and later on read in the frame buffer. There's some parsing going on and the parser doesn't expect '=' in the object name. I'll make a note to handle it properly.

[flat]

It looks like V-Ray 6.2 hasn't improved it yet.

[anna_kwacz]

Hello,

I have the same problem. When I want to add "cryptomatte mask" in V-Ray FB, there's message appears:
"no elements available". How can I fix it?
Thank you for your help!

[eunine_hsu]

anna_kwacz

The solution is the one above. Look for any element in your scene with the symbol '=' and delete or rename them. I just fixed it this way.

I searched for elements and found 4 geometries with the '=' character.

I renamed them, and my Cryptomate started working again.

thank you yavor.rubenov

[Vizioen]

yavor.rubenov was this fixed? Or are there any other reasons or symbols why cryptomatte would not be available (missing element) to add as a mask even though it's available in the list?

[Vizioen]

Ok, I found a new bug apart from the = bug (which I'm not sure is still there: I didn't test it as there were no objects in my scene with =).

I had to create a script that listed all the materials and it's submaterials in the listener to see if there were any weird symbols in the names of the materials of the objects being rendered, as I renamed all the objects with the object rename tool.

I found a material with a ";" (Semicolon), while I personally wouldn't name things with a semicolon some people apparently do and that caused the following problem:

No cryptomatte will work if there's a material with a ; in the name, so even if you have cryptomatte set to node name or node name with hierarchy it's not going to work, even though the render elements are there, you get missing render element if you want to use it in the VFB as a mask. I don't know what happens in compositing software I didn't test it. Removing the semicolon was enough to make it work again.

[Vizioen]

Not sure if this has been documented as a bug or do I have to open a new thread for this?

[yavor.rubenov]

Sorry for the delay - the original issue is not yet fixed unfortunately.
As for the semicolon - it is the same issue with unexpected symbols in the item names.