Question about saving to exr out of VFB.

[ChiefsFan]

In a Mograph lecture he mentions that saving out of VFB to exr can mess up cryptomatte or possibly ACES. I can't find the exact clip so I'm paraphrasing. Then in a thread I had read someone said that this was fixed. Can someone clarify if any of that is true?

If it is fine to save out a exr from VFB for cryptomatte and ACES color space could I do a region render then save it to exr if I forgot to unhide an object in my final render? Would everything be ok? Or will I have to render the entire scene from scratch?

I hope I was clear in my issue/question. Thank you for any advice.

[Muhammed_Hamed]

Hello ChiefsFan

Kamel talked about this in this lecture "0615_Compositing_RenderElements_In_Fusion_67"
He recommends writing the render to disk in Vray's RAW image format for Cryptomatte to work(without issues), instead of saving an EXR "out of the Frame Buffer" to a single file

Personally I save my renders out of the frame buffer to a single EXR and Cryptomatte works fine, I have been doing this for a long time (using ACES for nearly 2 years) see below





I think he is referring to an old issue in Vray Next, where we had to write EXRs to disk for the right metadata for Cryptomatte to work. I reported this to devs and it was fixed long time ago, since then I have always been saving EXRs out of the frame buffer. You could give this a try with your scene, it should work
And this old issue had nothing to do with ACES as far as I know
I also tested with render region, Cryptomatte works fine as well. You don't need to render the image from scratch

Best,

Muhammed

[ChiefsFan]

Thank you Muhammed_Hamed for taking the time to test, write this up and respond. Very kind of you and I really appreciate the clarification on everything!

Hope you have a wonderful weekend and stay safe.