CG into ACES comp, what profile?

Hi! I’m working on a project where we comp in ACES. The CG is rendered from 3Ds max (vray). In my comp I don’t convert the 3D but I do convert the live footage to ACEScg. I think this is correct but I don’t know for sure. The 3D guy says that there is no colorspace settings in his render so I guess he renders it in linear EXR.

Do anyone know if this is correct or are there some conversion I’m missing?

Vray supports OCIO, so it’s recommended to download the ACES OCIO implementation and set the V-Ray Frame Buffer to use it.
V-Ray OpenColorIO Support

There he can set the Input Colorspace to ACEScg, so both of you will see the same result (hopefully…). Otherwise the renderer would directly feed the image - with gamma correction - to the monitor, which isn’t ok for many reasons.

Additionally using ACEScg in the render view means that the relative primaries of the renderer are now defined and the input colour textures (even the linear ones), which are not in ACEScg should have a conversion with the VRayOCIO texture converter. Linear data textures like normal map, bump, specular intensity etc. doesn’t need this. I didn’t use this OCIO support in V-Ray, so I have no experience how it performs in practice…

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Thanks sciVfx for that information! I think i understand better the Vray workflow.
We also have some external 3D rendered with Octain. I can’t find any OCIO/ACES information for Octain, it seems like it’s not yet implanted.
What I do get is linear EXR files. Should I process these as ACEScg directly or something like Linear sRGB?

I have no experience specific to 3DS Max, but I have experimented with creating a LUT to simulate ACES Output Transforms in the viewport of the Octane Render plugin for Cinema4D. See this thread. If you want to try my LUT to see if it works in Octane in other software, send me a DM.

Interesting… So the pipe would be to apply the lut in the viewport and then render linear EXRs to comp? What would you set as input in OCIO for those images?

Correct. I do not know if Octane render gives exactly the same controls in 3DS Max as it does in Cinema4D. But if it does, it should be possible to apply the same process. Because Octane cannot render to a log image, and it appears that the post processes have no access to values >1, my approach uses a particular set of settings to produce a low contrast ‘pseudo log’ image in the viewport, and I derived LUTs which can be applied to that to give a reasonable approximation of the results of bringing a linear sRGB render from Octane into Nuke with the input space set to Utility - Linear - sRGB and using the ACES Rec.709 and sRGB Output Transforms respectively.

I was testing with the beta of Octane v4, which has LUT support.

Hi Nick, I messaged you last year but Octane 4 wasn’t fully out. I am relooking at ACES for C4D Octane (I use ACES in DaVinci Resolve). If you have anything new to share since last year that would be good. I will let you know how I get on if you are interested. Chris