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OCIO config file in Blender Part 2 - Organizing your OpenColorIo Configuration and adding ACEScg.

This is a direct follow up from the OCIO config file in Blender part 1. Please, read the first part in case of any doubts related to aspects of the config.ocio file or LUTS.


In this second part, I'll show you how to proper organize the OpenColorIO config file to avoid to mess the default Blender configuration. In this way, it's easier to change configurations or disable the OCIO configuration, if desired. Also, it will be shown how to add the ACEScg colorspace to the config.ocio file. In doing so, the artist will have the option to use the AgX colorspace or the ACEScg colorspace, without the necessity to have different configuration files.


This technique is also shown in my previous turorial on how to have different configurations for multiple render engines.


The idea here is to have the AgX colorspace and also the ACEScg colorspace available in the same config.ocio file. In this example, the ACEScg colorspace will be the default. The artist will have the option to change to AgX or use the Standard Blender colormanager configuration.


This is not a so difficult task, but the artist will have to have a basic knowledge on how to write a OpenColorIO config file. The rules can be seen at the OpenColorIO official documentation.


Here, I'll show what I did to have my own configuration. First, I copied the Blender 4 colormanager configuration to another folder. In this case, the C:/OCIO folder. The Blender original configuration is composed by the config.ocio file, plus the filmic and luts folder. I added the aces_luts folder for the ACEScg lut files, and the cinematic folder is the one shown in the first tutorial, which stores the lut files used as looks.


OCIO folder structure.
OCIO folder structure.

The first thing to alter in the config.ocio file is the search_path variable to include the cinematic and aces_luts folder.


Colon separates each folder.
Colon separates each folder.

Note that cinematic/BW means that BW, is a cinematic subfolder.


The next part is to configure the roles, which defines the default colorspace and color transforms setups.


A “role” is an alternate name to a color space, which can be used by applications to perform task-specific color transforms without requiring the user to select a color space by name.
A “role” is an alternate name to a color space, which can be used by applications to perform task-specific color transforms without requiring the user to select a color space by name.

The next pass is to configure the display devices. In this case, I added the ACES display to Blender's 4 config.ocio file.


This section defines all the display devices which will be used.
This section defines all the display devices which will be used.

Next, it's necessary to add ACES to the active displays and active views list. Both are to make the ACES option visible in Blender's UI.


"active_displays": for all displays to be visible, and to respect order of items in displays section; "active_views": for all views to be visible, and to respect order of the views under the display.
"active_displays": for all displays to be visible, and to respect order of items in displays section; "active_views": for all views to be visible, and to respect order of the views under the display.

I also added the ACES config in the colorspaces section, of course. I copied and pasted from a previous configuration file.


This section is a list of the scene-referred colorspaces in the config.
This section is a list of the scene-referred colorspaces in the config.

The next section is the Looks section, which defines a list of “looks”. This section is optional and I added some LUTs for the ACEScg colorspace, using the same method shown in the first tutorial.


Adding LUTs as looks for the ACEScg colorspace.
Adding LUTs as looks for the ACEScg colorspace.

Note that I used Input - ADX - ADX10 as process space, which is LOG in ACEScg. The .cube LUT files are in LOG. It's recommended to use LOG when using LUT transforms in Blender, to achieve more consistent results. Again, see the first tutorial for more details.


In the tutorial How to have different configurations for multiple render engines in Blender 3D, I've shown how to create a .bat file to launch Blender with specific configurations. I used the same method to load the config.ocio file located at the C:/OCIO folder. This is a pretty much clean way than to mess up with Blender's colorspace original files. If you have any doubts on how to create a .bat file, please read the tutorial mentioned right above.

I have a .bat file named Blender_vanilla.bat located at C:/. This is the file's content:


The .bat file loading a custom OpenColorIO configuration.
The .bat file loading a custom OpenColorIO configuration.

The first line, SET OCIO=C:\OCIO\config.ocio, loads the OpenColorIO configuration shown in this tutorial.

The second line defines C:\BlenderCFG\4.0 as the folder to store the Blender start up configuration.

The third line sets the C:\BlenderScripts\4.0 folder to store the artist custom plugins.

Finally, the last line launches Blender.

Of course, this is using my chosen paths. The reader must use his/her own chosen paths.


The beauty of this is that is very easy to maintain and modify. Also, the artist can use this OCIO config in Blender 3.x !

The .bat file method is also better than to set up an OCIO environment variable, because a system wide variable will affect any 3D software. Using the .bat file only affects the running software. Again, for a complete workflow on how to create a .bat file and call it from a shortcut, see the How to have different configurations for multiple render engines in Blender 3D tutorial.


Now, the artist can choose between ACEScg and AgX colorspaces inside Blender 4... or Blender 3.


Using the ACEScg colorspace.
Using the ACEScg colorspace.
Using the AgX colorspace. Both AgX and ACEScg can also be used in Blender 3.x.
Using the AgX colorspace. Both AgX and ACEScg can also be used in Blender 3.x.

What's Next?


It's available for download on the Slick3d.art Gumroad page the OCIO configuration used for this tutorial. The artist will get a OpenColorIO configuration with the AgX and ACEScg colorspaces, plus ten cinematic Looks. Down below it's a render done in ACEScg comorspace using the Batman vs. Superman look.



One last thing you should know:


Slick3d.art was selected as one of the Top 20 3D Art Blogs on the web by FeedSpot. It is a great victory to me. It is a huge effort in very hard times. Besides, Slick3d.art encompasses my love for design and writing that started in my teen years. I am very grateful for the recognition that was a total surprise. Click here to go to FeedSpot Top 20 list or click on the image down below.


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