Why does this error appear?
The default 3ds Max OCIO color management mode includes color transforms as part of its configuration, and these transforms often incorporate tone mapping or view transforms that achieve similar goals to the Corona ACES OT tone mapping operator. When ACES OT is applied on top of an existing view transform, the result is that the color data is transformed twice, leading to visual inconsistencies and incorrect results.
In other words, when using the 3ds Max OCIO color management mode, an effect similar to the Corona ACES OT tone mapping operator is always applied to the rendered image. If you use both the 3ds Max OCIO color management mode and the Corona ACES OT tone mapping operator, this results in applying the effect twice.
How to Resolve the Issue?
To get rid of this error and ensure accurate color output, you can choose one of the following solutions:
1. Disable the Corona ACES OT tone mapping operator:
If you want to use the existing 3ds Max OCIO color management mode with its view transform, disable ACES OT in the Post tab of the Corona VFB. This avoids duplicating the color transform.
2. Switch to Gamma Workflow:
Alternatively, switch from the 3ds Max default OCIO color management mode to Gamma Workflow. Gamma Workflow is the legacy color management mode. It assumes that the monitor primaries are Rec.709/sRGB and it does not incorporate view transform, so it is correct to apply the Corona ACES OT tone mapping operator to the rendered image.
Examples
3ds Max OCIO color management mode enabled. ACES OT enabled. The image appears darker and the highlights are heavily clamped. The error message is displayed in this case:
3ds Max OCIO color management mode enabled. ACES OT disabled. This is the expected appearance of the rendered image:
3ds Max Gamma Workflow color management mode enabled. ACES OT enabled. This is the expected appearance of the rendered image: