When using the 3ds Max OCIO Color Management Mode, the rendered image looks different directly in the Corona VFB than when saved as a Corona EXR (.CXR) file and viewed in the Corona Image Editor or other software. This article explains why.
When using the legacy 3ds Max Gamma Workflow Color Management Mode:
- In the Corona VFB, the image is rendered in the color space set by Corona settings, transformed back to linear sRGB, then tone-mapped and post-processed (white balance, contrast, bloom and glare, etc), and finally gamma-corrected.
- When you save your render as a CXR file, it is actually saved without any tone mapping or postprocessing effects applied to its pixels. The Corona tonemapping and postprocessing effects are stored as additional metadata in the CXR file.
- When your open the CXR file in the Corona Image Editor, all the Corona tonemapping and postprocessing effects are applied based on the additional metadata and the image is then gamma-corrected.
- Only the sRGB color space is available for previewing the render.
- Only gamma correction is available as view transformation (linear sRGB to gamma-corrected).
Because of the above, when using the legacy 3ds Max Gamma Workflow Color Management Mode, the results in the Corona VFB and Corona Image Editor look the same.
When using the 3ds Max OCIO Color Management Mode:
- In the Corona VFB, the image is rendered in the color space set by 3ds Max Color Management and then previewed based on display color space and view transformation settings. Display settings define the color space of the monitor to which the rendered values are transformed, then Corona tone mapping and post processing is applied, and then view transformation is applied.
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sRGB, DCI-P3, AdobeRGB and other color spaces are available in 3ds Max for displaying the render.
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ACES 1.0 SDR-video, Log, Raw and un-tone-mapped view transformations are available in 3ds Max.
- You can use even more options by loading a custom OCIO config file in 3ds Max Color Management.
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sRGB, DCI-P3, AdobeRGB and other color spaces are available in 3ds Max for displaying the render.
- When you save the render to a CXR file, it is saved without any Corona tone mapping or post processing applied. Instead, this information is stored as additional metadata in the CXR file. The render is saved in sRGB color space, 3ds Max view transformation is ignored.
- When you open the CXR file in the Corona Image Editor, all the Corona tonemapping and postprocessing effects are loaded based on the additional metadata, however the 3ds Max-specific color management settings cannot be applied outside of 3ds Max.
Corona Image Editor (and other software too) do not have these specific 3ds Max display/view transformation options, and because of this and the above, the image you are viewing in the Corona/Max VFB and a CXR you open in the Corona Image Editor look different.
If we would save the image as CXR with the 3ds Max-specific tone mapping "baked" into all image pixels and then open it in the Corona Image Editor, that would result in an incorrect appearance since we would be applying the Corona tone mapping and post processing effects after the 3ds Max-specific tonemapping, which is the wrong order of operations.
Solutions/workarounds:
- If your priority is using the 3ds Max OCIO Color Management Mode, saving the image in the CXR format, and being able to later adjust its tone mapping and post processing settings, the solution is to load it into Corona VFB 2.0. This is possible only in Corona 12 and newer. In this scenario, if you load the CXR file into the Corona Image Editor, it will always look different than in the Corona VFB.
- If your priority is making sure that the image you see in the Corona VFB and the one in the Corona Image Editor are identical, you need to use the legacy 3ds Max Gamma Workflow.
Other ideas to consider:
- Saving to a low dynamic range format (e.g. png, jpg) - in this case the image will appear the same in the VFB and in any picture viewer or 2D editor after saving.
- Saving to EXR format and using the 3ds Max output conversion options - this should ensure that the display/view transformations are embedded in the output. Opening such image in specialized software with necessary settings (color space conversion and display-view transformation) should give the same result as in 3ds Max.