Cryptomattes and Environment fog

[Yannick]

Hi, is there a way for the environment fog not to affect the cryptomatte aov?
My cryptomatte pass doesn't have solid color as the fog darken the pass.
Thanks.

[Buck]

I generally run cryptomattes and other tech buffers in a separate tech/utility render. That way for lighting and shading iterations I'm not constantly running out the much larger cryptomatte passes (which are 32 bit). Only re-run them when animation has changed.

If you do that, you can turn off environment fog for the utility pass.

[SonyBoy]

Doing a separate tech/utility pass has become standard production procedure. However, I was once informed by someone at Chaos, somewhere on this forum, that in order to be as accurate as possible mattes need to be rendered with the beauty calculations. Not sure if they were making a blanket statement that in practical terms is only a consideration in certain situations (e.g. where certain raytraced effects like refraction need to be calculated), and whether there is a "tolerance" threshold for this that can be managed. But I have personally experienced some gotchas with trying to break out these types of passes, so be careful with things like disabling shading or lighting calculations for a tech pass, thinking they aren't necessary.

[hermit.crab]

Thanks for the report. I've logged the Cryptomatte darkening as an issue (internal bug-tracker id: VGPU-5737) for our developers to investigate. You may need to render twice as a workaround.

EDIT: The issue seems to concern GPU rendering only. Switched log id.

[Yannick]

Hi, thank you for your answer. Like SonyBoy, I though it was better to render the cryptomatte aov with the beauty for better result. i'll try to render the aov with my deep pass.

[Buck]

I generally just use a blank dome light for my Utility passes. That seems sufficient for sampling.

[Tyros]

Interesting that the cryptomatte works with the fog type ->VRayAerialPerspective
but not with the VRayEnvironmentFog

[lukepenry]

Has this been fixed yet??? i still get fog affecting my cryptomattes. Vray GPU

[hermit.crab]

Has this been fixed yet??? i still get fog affecting my cryptomattes. Vray GPU

Not quite yet. Thanks for the feedback, though. I've made some updates to the log and will forward it to the developers so as to bump its priority.