(Fixed) [HOU-2889] Alembic Issue with Cryptomatte

[ronald_a]

Hi there,

I found an issue that is connected to alembics and cryptomatte:

When using alembics with baked in material paths where one packed alembic holds multiple materials and DOF or motionblur is used, the sampling quality of the cryptomatte is poor in the areas of overlapping materials of the same packed primitive and the objects are out of focus/ motionblurred.

Here are two images of the same thing, one rendered with alembics, the other one with unpack geometry. in the image with the issues, you can see that the purple mask is ok at its left side. That is because it is overlapping with another object (pack alembic). where it is not ok, its overlapping with the same alembic.

I did an official support case for this as well where I uploaded a scene that demonstrates the issue.

[tsvetomira.girginova]

Dear ronald_a, hello.

Thank you for providing a test scene via our support mail.
I will take a look, discuss with the team what may cause it and contact you back.

Thanks for reporting.

[ronald_a]

tsvetomira.girginova is it possible that this has been fixed already in the latest nightly? in my testscene the cryptomatte seems fine now.

[tsvetomira.girginova]

Hello again,

I have just tested with nightly builds from 14 & 15 December and the issue is still there.
Could you share the exact V-Ray build information?

I suspect that something has changed in your setup to receive equal results.

[chakarov]

Hello ronald_a , I've reproduced the problem in a clear scene with simple meshes. I've reported it and will write back here once I have more info from the devs.

[ronald_a]

chakarov ah, great, thanks for looking into it. Hope this is an easy fix.

[tobiasroesli]

Hi,

I think there's another issue with the Cryptomatte.

Can you guys have a look:
https://we.tl/t-QEw5A10dhX

Cheers
Tobias

[Gosho.Genchev]

Hey tobiasroesli ,

Could you please clarify what the issue is with the screenshot above? I checked your scene and I see that there's a partitioned alembic generating 2 separate cryptomatte colors for each alembic shape when in "Proxy Sub-Object" mode - is that what is giving you trouble?

Best regards!

[tobiasroesli]

Hello Gosho.Genchev ,

the Problem is that the Cryptomatte has jagged edges, no anti-aliasing. I don't know why. Is it my fault or is there a problem with the geometry or is it a bug?

Cheers,
tobias

[radoslav.platikanov]

Hi Tobias,

The issue here is that there's no light in the scene and the RGB is black. This prevents the adaptive sampler from properly sampling the image as it only sees the empty RGB and the Alpha. You can try increasing the min. subdivs in the image sampler, or just render with lights.

[Dubbie99]

I have struggled with this a lot on a recent scene where I had an object that was roughly the same color as another in the RGB, so it was sampled very crudely. This meant the cryptomatte quality was very poor.
I would love a checkbox in the cryptomatte element that says "Consider for AA"

[tobiasroesli]

Hi radoslav.platikanov ,

yeah, this fixed the problem.

I just tought I do a Cryptopass which renders fast because when you do Deep stuff you can't render it together.

Thanks for the help Radoslav!


Cheers
Tobias

[david.anastacio]

Hi tobiasroesli,

When I need to render one of this utility passes that need sampling just for the AOVs, I override all materials with a self illuminated shader with a falloff map so all edges fallogg to white so they have decent sampling and renders super fast.

Best,
David.

[tobiasroesli]

Hello david.anastacio ,

that's a very handy trick, thanks a lot!!!


Cheers!
Tobias