Author Topic: Corona Cryptomatte  (Read 1111 times)

2022-11-07, 05:48:27

UsmanS

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Hi, I was recently looking into corona cryptomatte and how it works. I have added in the render element. In the render I can see all the different colours and then when I bring it in photoshop using EXR-IO it brings in everything with the masks, but all the masks are black and doesnt have any information in them. The cryptomatte still looks the same it did in max. Am I doing something wrong here ?

2022-11-07, 14:14:41
Reply #1

TomG

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Doesn't look right as the cryptomatte passes should not be divided into rgb and a, and they should have names after them of objects, see attached. Anyway, we'd need lots of info here as there are various steps:
- What does your Cryptomatte set up in Render Elements look like?
- How did you save the files? From the VFB, from somewhere else?
- You did save to CXR, and not EXR, right?
- What are your EXR-IO settings?

Thanks!
   Tom
Tom Grimes | chaos-corona.com
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2022-11-07, 14:15:30
Reply #2

TomG

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PS, always ignore the colorful RGB layer from the Cryptomatte, it's of no use and is just a byproduct :)
Tom Grimes | chaos-corona.com
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2022-12-01, 14:17:13
Reply #3

Blanco

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Hi Tom
I was wondering if you could talk me through the process of extracting different items to make layers in Photoshop using exr-io. I have tried and failed numerous times....
Thanks

2022-12-05, 17:05:22
Reply #4

TomG

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- Add Cryptomatte layer into the render elements (see "cryptomatte save" image)
- Render, then save to CXR (same image as above)
- Rename CXR to EXR
- Open in Photoshop with EXRIO (see "tom exrio settings" image )
- Hide all layers to leave just the desired mask
- Select All and Copy (see "cryptomatte select all copy" image)
- Remove the Select
- Re-enable the RGB layer, and add a layer mask
- Alt click on the layer mask to enter editing mode of the mask (https://studioratonline.com/blog/paste-into-layer-mask-photoshop/ )
- Paste the copied cryptomatte mask into the layer mask
- Alt click the layer mask to return to viewing the layer and not the mask, and now you have that individual object masked out (see "cryptomatte alt click mask and paste" image)

Repeat by duplicating the Beauty RGB and adding a mask for other objects you want to process separately (or layers, etc. - there is no by materials option yet), and of course layer those onto a Beauty with no mask (haven't set that up in the screen grabs). Apply adjustment layers to the masked-out layers so you can adjust them as needed, e.g. change their color.

Or can do this not for the Beauty layer but for Reflection, Refraction, Direct, etc. if you have added those, e.g. to control the reflections in a mirror separately from the other objects. Note that other masks can do this particular example and likely more easily; cryptomatte really only offers benefits when using things like DOF or Motion Blur, where the masking is better with Cryptomatte as it accounts accurately for the "soft edges" in the blurring.

Also note tone mapping will have to be done in post and is best left at defaults in the render.
« Last Edit: 2022-12-05, 17:09:02 by TomG »
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2022-12-07, 15:56:42
Reply #5

Blanco

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Thanks Tom
I'll give that a try

2022-12-07, 16:07:54
Reply #6

TomG

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You're welcome, let us know how you get on!
Tom Grimes | chaos-corona.com
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