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Working with RCM DaVinci Wide Gamut/Intermediate for VFX

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shebbe

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Working with RCM DaVinci Wide Gamut/Intermediate for VFX

PostTue Aug 16, 2022 11:41 am

Hello,

As a follow up to a recent post someone had on getting the Fusion viewer to match Edit/Color page with RCM I decided to put it out here. I'm aware of the shortcomings of ReFusion but it's not completely designed without thought.

The problem:
RCM forces a linear workflow in Fusion in the sense that it will assume the linearized version of chosen timeline color space for whatever media you are using. This means DaVinci Wide Gamut/Linear for example when choosing the DWG/Intermediate preset in RCM. It makes sense for a VFX workflow because you want to work in the working gamut/linear anyway. But of course it creates a problem because you don't want graphics or other display referred data to be tone mapped afterwards by the rest of the pipeline. But I'm not addressing that part here.

Fusion lacks any form of proper support for any possible gamut and transfer functions, nor display rendering transforms to inject into the Fusion viewer to mimic RCM's display transform. This is the one I do address.

Sloppy workaround:
Mimic the DRT behind the MediaOUT node with Color Space Transforms. While this works, it's a major annoyance for measuring values whilst looking through DRT and previewing nodes in the tree itself.

Solution:
Fully mimic the RCM pipeline via LUTs.
From the VFXStudy YT Channel I gathered that the data should first be corrected first with lin to log.
We can achieve this by creating 1D shaper LUT from Linear to DaVinci Intermediate.
Unlike the node tree, Fusion's viewer OCIOFileTransform supports only 16bit int so a spi1d is unusable.
We can load it directly as .cube LUT however. It seems that Resolves VFX IO folder also uses cubes for 1D LUTs so I transferred the spi1d data over to that format and placed the LUT in that folder.

Then I created the display transform with a CST with the proper settings and saved it as a 3D cube.
We can now load the Linear to Intermediate LUT and then right-click the viewer -> LUT..->Add New and pick the DRT LUT there to add it as second LUT.

Now the viewer looks identical to the Edit/Color page and you can work in Fusion as you'd expect.

2022-08-16 13_26_21-Window.png
2022-08-16 13_26_21-Window.png (871.82 KiB) Viewed 836 times

One small caveat is that you shouldn't use this LUT in your actual pipeline because the lin to log only covers 0-100 linear range so if your plate has negative values they will not be represented. It shouldn't be too much trouble for a viewer.

So here are the LUTs I used hope people find it useful.
Anyone using this workflow but with ARRILogCv3 as timeline space instead can use the existing Linear to LogC LUT in VFX IO folder and create the respective DRT LUT to go on top instead.

Ultimately imo it would make much more sense to get rid of all the non-maintained IO LUTs, Fusion's gamut node and managed viewer settings and replace them with CST to have access to the full list of gamuts and transfer functions in sync with what Resolve itself offers, but who knows when that will happen.
Attachments
Linear_to_DaVinci_Intermediate.zip
(83.35 KiB) Downloaded 98 times
DaVinciDRT DWG Intermediate 4000nits to Rec.709 2.4.zip
(257.92 KiB) Downloaded 97 times
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Douglas Bischoff

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Re: Working with RCM DaVinci Wide Gamut/Intermediate for VFX

PostSat Nov 12, 2022 6:55 pm

This was hugely helpful in getting standalone Fusion to view Linear EXR files from Resolve DWG/Intermediate into Rec.709 space for VFX work.

Thank you very much!
Douglas Bischoff
Ceridwen Productions

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