How does Cryptomatte work?

[dgruwier]

Not as in "how do I use it", but "how does it work technically"?

Using something like Render ID also creates a shade of color per ID, but doesn't support blending colors (aa, motion blur, dof), since you wouldn't be able to accurately isolate the colors at the edges as they mix with each other. What does cryptomatte do to get around this? It's still just an image file with RGB values right?

[Moriah]

I would like to know this too!

Also, how does someone import this in Fusion?

[instinct]

The poster outlines the technical basis: https://github.com/Psyop/Cryptomatte...tes_poster.pdf

The repo also has fusion code: https://github.com/Psyop/Cryptomatte

[Moriah]

instinct i tried installing the fusion code but nothing appears on the tools (Fusion Free btw, but i think it supports it, since it's not an OFX).

[dgruwier]

instinct That is perfect, exactly what I was looking for. Thank you!

[instinct]

Moriah : I am not using fusion myself so i cannot really help beyond pointing at the repository i am afraid

[vlado]

I'll see if we can add some guides in the docs to get things up and running in Nuke and in Fusion.

Best regards,
Vlado

[DENEB]

Moriah to use cryptomatte with V-Ray in Fusion

first render a scene with VRAY 3.6 with cryptomatte render element
Important: you have to write the EXR from the V-Ray raw image in the framebuffer rollout in V-Ray tab in the render setup dialogbox, don't try to save direct from the VFB that does not work.

1) install FUSION 8.x
2) get the cryptomatte file on the GitHub
3) copy
- lmurmurhash3.lua
- simplejson.lua
- struct.lua
to C:\Program Files\Blackmagic Design\Fusion 8
4) copy
- cryptomatte.fuse
to C:\Program Files\Blackmagic Design\Fusion 8\Fuses
5) Start Fusion
6) create a loader and load your EXR, copy this loader to have two
7) In the first loader right click and select insert tools / cryptomatte / cryxptomatte (this will change automatically the channel assignement of your loader, without that nothing is working )
8 ) Assign the cryptomatte1 node/tile to one of the fusion viewport
9) Then move the small red axis to the object you want to matte and click the Add button
10) Your object is selected with correct AA
11) Now add an effect to the second loader for exemple colorcorrect (rightclick - insert tools / color/ colorcorrector)
12) Set some color correction for test in ColorCorrector1
13) Then add the output of the cryptomatte to "ColorCorrector1.effect mask"
14) Assign the ColorCorrector1 to one of the fusion viewport

You got it your object is color corrected with perfect AA

Now you can play with the Cryptomatte1 to add more object to your mask

Best regards
PA

[Moriah]

DENEB im getting this error after copying the files you mentioned and launching Fusion 8. Any idea?

[gandhics]

Download zip and unzip and install.
If you save as from browser, browser add unneccesarystring.

[Moriah]

That worked, thanks to both of you!

[stevesideas]

Thanks for the tip on installing. I'll be interested to see this working within Fusion. Could prove to be very very useful.