if you use OCIO, then when you open the scene, the render colors change randomly

[Yuriy Bochkaryov]

Below are 2 pictures, this is the same scene, all textures use the Corona bitmap shader, the color profile is set to ACEScg, I render, save the picture, restart 3D Max, load the scene again, render and the picture has different colors, there are always options 2, either more saturated colors, or more calm ones, as if there are 2 profiles in the scene and 3D Max randomly chooses which one to use every time the scene is loaded - this is a big problem
how to work in a scene where you don’t know what colors you will have the next time you load 3D Max

[Aram Avetisyan]

Hi,

Thanks for checking this. As a small part of Color management is not supported, I would like to ask you to send the scene, or any other sample scene where the issue can be reproduced, so we can have a look.

As I understand, the reproduce the issue, the scene just needs to be opened, rendered, saved, closed, then re-opened and rendered again. The results should ALWAYS vary? Or some of the times? Or it changes between the options you mentioned?

[Aram Avetisyan]

Here is the Color Management article:
https://support.chaos.com/hc/en-us/articles/20474209561617-Color-management-in-Corona-for-3ds-Max

Feel free to skip the theory part and go to the very bottom for Corona specific details, supported and unsupported things.

Nevertheless, if the scene and settings are the same, if the scene is opened, rendered (result A), then closed, reopened and rendered (result B), the renders should be pixel perfectly the same - A = B.

Please attach a sample scene so this can be tested. Or you can share some basic reproduction steps.
If you have time, please give it another try with Corona 12 Daily Builds - there may be updates which cover this case.

[Yuriy Bochkaryov]

Hi,

Thanks for checking this. As a small part of Color management is not supported, I would like to ask you to send the scene, or any other sample scene where the issue can be reproduced, so we can have a look.

As I understand, the reproduce the issue, the scene just needs to be opened, rendered, saved, closed, then re-opened and rendered again. The results should ALWAYS vary? Or some of the times? Or it changes between the options you mentioned?

Hi Aram
yes, you understood correctly, you need to open it - render, then restart, open it again to render, sometimes the color changes on the second try, sometimes on the fifth, it’s not stable, but there are always 2 color options
I'll post the scene later

there is also a problem with changing the color - the scene is in Gamma Workflow, I switch to OCIO ACEScg, render, save the picture, save the scene, restart 3D Max, load the scene, start rendering and I already have different colors in the picture
these colors remain after restarting 3D Max, the problem is only when you switch from Gamma Workflow to OCIO ACEScg - then the render comes with the wrong colors, that is, after switching to OCIO ACEScg you must always first save the scene, then restart it in 3D Max
I attached a video
Another problem - the scene is in Gamma Workflow, I switch to OCIO Rec.709-sRGB, I start the render and an error appears, the render does not start, you need to save the scene, restart it in 3D max and then it will start rendering, I also attached the video to the scene
try to repeat what I showed in the video in my scene

Video - https://disk.yandex.ru/d/tns-QpfHVUpB4Q

[Aram Avetisyan]

Hi,

We need to make a few things clear from the video.
If any of the points is wrong, let me know:

First (left) video (the second/right video with Rec709 rendering space is a different thing, so let's leave it for now):

1. The scene is started with Gamma workflow - the render is expected
2. OCIO with ACEScg rendering space is selected - the render is changed and IS EXPECTED. This is because in OCIO mode Corona VFB does not support view transform - the result is always linear (darker, contrasty). Yet in Gamma workflow simple Gamma transformation is applied. This is mentioned in the Color Management article as well. So everything is fine here, the color change is expected.

The unexpected/weird thing with the other color change - specifically for the saturated highlights - is what needs to be investigated further.
I can confirm reproducing it solidly, and it is related to the "Reset" action in 3ds Max.

1. Reset max
2. Open the scene
3. Render - result A
4. DO NOT Reset max, re-open the scene
5. Render - result B; result B is different than result A, even though it is the same file, without changes.
6. If the scene is opened WITH Reset first, it will give the same result A, every time.

This will be reported surely. It may be 3ds Max resetting/changing some settings, and/or Corona not seeing them.

Hope this clears things out.

(Internal ID=1284057372)

[Yuriy Bochkaryov]

Hi Aram
I checked - the problem is really only if you use the "Reset" function in 3D Max, then when you reload the scene, the color management still shows the OCIO mode, but when rendering we have different colors, the colors of the Unmaneged mode
and it’s good news that we found the problem, now I know which of the color options is correct and which is incorrect