OCIO / ACEScg

[mrsacan]

Hi guys

I'm used to work on gamma 2.2 workflow and I don't use OCIO. Recently I installed 3ds Max 2025 and it says gamma 2.2 setting is legacy so I wanted to start work with OCIO (because legacy usually means at some point it's going to become obsolete and not supported), but first of all I can't get colors right (corona bitmap).
I attached some screenshots. I tried different color spaces, but it's always different.
I checked some old topics and this link : https://support.chaos.com/hc/en-us/articles/20474209561617-Color-Color-space-and-Color-Management-Basics
But I didn't able to see a solution/workflow.
I can still use gamma workflow and do my job, but I want to learn how can I setup OCIO / ACEScg correctly. Is it possible or not etc.

[Aram Avetisyan]

Hi,

Which version of Corona are you using?

There were related fixes which should be in latest Corona 12 Update 2 release candidate. If possible, please try with it.
I suppose your veneer texture has nothing special and should be with sRGB primaries.

[maru]

RGB primaries set to "auto" should give you the correct results.

[mrsacan]

Which version of Corona are you using?

There were related fixes which should be in latest Corona 12 Update 2 release candidate. If possible, please try with it.
I suppose your veneer texture has nothing special and should be with sRGB primaries.

12 update 1 (hotfix 1)

[mrsacan]

RGB primaries set to "auto" should give you the correct results.

My last screenshot is set to auto, maybe I'm missing something else in another screen/option?

[maru]

Is your texture using an ICC profile? If yes, then the issue is that 3ds Max / Corona is not ICC-aware.
Recently there was a discussion about this.

[piotrus3333]

RGB primaries set to "auto" should give you the correct results.

first time loading a bitmap into CoronaBitmap follows ocio rules (sRGB by default) but then selecting Auto gives incorrect result (Linear sRGB in this case).

and why there is no "gamma 2.2 sRGB" in the drop down options? this would be the natural option to pick for users coming from old 3dsMax versions.

[maru]

RGB primaries set to "auto" should give you the correct results.

first time loading a bitmap into CoronaBitmap follows ocio rules (sRGB by default) but then selecting Auto gives incorrect result (Linear sRGB in this case).

and why there is no "gamma 2.2 sRGB" in the drop down options? this would be the natural option to pick for users coming from old 3dsMax versions.

What the hell. It looks like if you load a jpg bitmap into the Corona Bitmap loader for the first time, it follows the rules set in 3ds Max. If you click "load map" and:
- double-click on your file or select your file and press enter - all is fine, it follows the 3ds Max rules
- just press enter without clicking anywhere with your mouse - then it sets RGB primaries to ACEScg
I have a weird feeling this is a 3ds Max bug, but I have logged it for our devs to investigate...

(Report ID=CMAX-1670)

[maru]

Going back to the original issue: please correct me if I am wrong, but as far as I know, once you use the 3ds Max OCIO workflow, it globally applies an output transform similar to our ACES OT. This means that the images will always appear darker/different in the material editor than in the Windows picture viewer or Photoshop. You can override this in 3ds Max color management settings by unchecking "material editor" under "displays and views" and setting its view transform to "un-tonemapped". This will only change the way bitmaps are displayed in the material editor though.

If you do not specifically need to use the 3ds Max OCIO mode for some reason, I would advise sticking to the gamma workflow. If you prefer the OCIO "look" for your final image, then you can simply enable the ACES OT operator in the Corona VFB.