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HOUDINI/REDSHIFT...is it possible to render ONLY Cryptomatte?

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Hi everyone,

I'm newbie to Houdini and Redshift... I need your help!

I failed to render Cryptomatte with correct object ID, and want to re-render only Cryptomatte without rendering main images to save time. 

Is it possible or is there any way to skip rendering main images? 

I just don't want to waste time to render the same images again.....

I appreciate your help!


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No, I don't believe you can. Cryptomattes are calculated at rendertime as an AOV output only.  There doesn't appear to be a cryptomatte shader that you can assign directly.
You could just setup your own matte pass the old fashioned way with Redshift matte shaders, but this wouldn't be compatible with cryptomattes since they would not have the associated metadata.
If you main renders are pretty heavy, you can try running an alternate version with cryptomattes enabled, and then remove lights and and extra geo that wouldn't contribute to the cryptomattes.

Hope this helps,

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As Dave says. not exactly, but you can definitely speed up re-rendering. Generally I set up two separate ROPs. One is a lighting render with only lighting AOVs (diffuse, spec, refraction, emission, etc). Then I have a separate ROP for utility passes (N, P, motion vectors, depth, crypto, etc). On that ROP go to "Objects" and exclude all lights. Turn off GI. And under "Advanced > Globals" turn off anything you can (Reflections, refractions, subsurf). Sometimes you need those for certain compositing things, but usually you can get away with out em.

Depending on how you've got Cryptomatte set up (if you're using IDs instead of generating mattes by texture) you can even force a default clay shader over everything).

I can usually get even pretty complex scenes down to a minute or so per frame.

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