Unreal OCIO Setup

A key component of virtual production is maintaining consistent colour across the entire rendering pipeline. This page covers the steps required to set up OpenColorIO (OCIO) in Unreal Engine to achieve consistent colour management throughout the production process.

Before proceeding, ensure you have finished setting up the project by following the steps in UE Project Setup.

Requirements

RenderStream Plugin

• See UE Project Setup | Plugins for details on setting up the RenderStream plugin.

OCIO config file

• Place your chosen OCIO config file into the Content folder of your chosen Unreal Project.
  • RenderStream Projects/<UEProject>/Content/<OcioConfig>.ocio
• A standard OCIO config file can be downloaded from the OpenColorIO GitHub.

Warning

Both Unreal Engine and Designer must use the same OCIO config file to ensure colour consistency.

OpenColorIO Configuration

To use OCIO, Unreal requires an OpenColorIO Configuration to specify which specific file and colour spaces you would like to use.

Adding a new configuration

1. Open the Content Drawer.
2. Click the Add button.
3. Navigate to Miscellaneous > OpenColorIO Configuration and select it.

Add OpenColorIO Configuration

Prepare colour spaces

Next we need to expose the relevant colour spaces from the OpenColorIO Configuration to configure the colour spaces in the RenderStream Plugin.

1. In the Content Drawer, double-click the OpenColorIO Configuration you just added.
2. Under Config, set the Configuration File to the .ocio config file you added from the OCIO Config File section.
3. Add the Desired Color Spaces and Desired Display-View to expose the colour spaces and display-views for later use.

OpenColorIO Configuration Settings

Desired Color Spaces

Exposed Desired Color Spaces are typically used for source colour spaces in RenderStream plugin:

• Unreal Engine uses sRGB / Rec709 by default as the Working Color Space in Project Settings.
  • The corresponding colour space in the OCIO config is Linear Rec.709 (sRGB).
• Another typical Working Color Space is ACES AP1 / ACEScg.
  • The corresponding colour space in the OCIO config is ACEScg.

Desired Display-View

Exposed Desired Display-View are typically used for destination colour spaces in RenderStream plugin:

• Rec.2100-PQ - Display - Un-tone-mapped is recommended for common RenderStream use cases.
• The destination colour space refers to the colour space in which content will be sent over RenderStream

Project Settings

Once the OpenColorIO Configuration is set up, we must configure the Project Settings to apply the colour transforms properly.

Navigate to Edit > Project Settings.

Engine - Rendering

In Project Settings, under Engine > Rendering, you can define the Working Color Space of Unreal Engine. All textures in Unreal Engine must match the colour space set as the Working Color Space.

For example, if the Working Color Space is ACES AP1 / ACEScg, then all textures must be in ACES AP1 / ACEScg. By default, Unreal uses sRGB / Rec709.

We advise sticking with Unreal Engine default colour space unless its strictly necessary to use a different colour space.

Engine Rendering Settings

Note

For more detailed information on colour spaces in Unreal Engine, refer to this Epic documentation - Color Pipeline.

Plugins - Disguise RenderStream

To avoid unintentional colour transforms, it’s crucial to enable and configure OCIO with the desired colour spaces.

1. Navigate to Plugins > Disguise RenderStream.
2. Expand the OCIOConfig section.
3. Select the Is Enabled checkbox.
4. Set the Configuration Source to the OpenColorIO Configuration you created earlier. (See: Adding a New Configuration).
5. Set the Transform Source to match the Unreal Engine Working Color Space.
   • Ensure the colour space is exposed in OpenColorIO Configuration (See: Prepare colour spaces).
   • Refer to Transform Source for matching colour space between Unreal Engine and OCIO.
6. Set the Transform Destination to match the Input transform of the RenderStream asset in Designer.
   • The colour space must be between 0 and 1.
   • Rec.2100-PQ - Display - Un-tone-mapped is recommended for normal use cases.
   • See: Set Input Transform on RenderStream Layer.

Plugins - Disguise RenderStream Settings

Transform Source

UE Working Colour Space	Matching OCIO Config Colour Space
sRGB / Rec709	Linear Rec.709 (sRGB)
ACES AP1 / ACEScg	ACEScg

Warning

Unreal Engine provides a UE > Working Space option for OpenColorIO Configuration, but this may not produce accurate colour in RenderStream.

Camera Actor Settings

Unreal Engine applies several post-processing effects which change colour grading. To maintain consistent colour through the rendering pipeline, it’s important to disable any unnecessary settings affecting colour.

1. Open the Details section of your CameraActor or CineCameraActor.
2. Navigate to Post Process > Lens > Bloom
   • Set Intensity to 0.0.
3. Navigate to Post Process > Lens > Exposure
   • Set Metering Mode to Manual.
   • Set Exposure Compensation to 0.0.
   • Set Apply Physical Camera Exposure to Untick.
   • Set Min EV100 and Max EV100 to 1.0
     • This will disable auto exposure of lens.
4. Navigate to Post Process > Lens > Image Effects
   • Set Vignette Intensity to 0.0.
5. Navigate to Post Process > Color Grading > Misc
   • Set Blue Correction to 0.0.
   • Set Expand Gamut to 0.0.
   • Set Tone Curve Amount to 0.0.

OCIO settings in Designer

After configuring Unreal Engine, you must set up the colour settings in Designer accordingly to produce a consistent colour.

Follow the OCIO page to configure Designer, but with specific focus on matching the OCIO config file and the Input transform of the RenderStream.

Importing OCIO Config file into Project

It is recommended to use the same OCIO config file for both Unreal Engine and Designer.

Alternatively, ensure that the OCIO config file contains the same colour space used in the Transform Destination in Unreal (See: Plugins - Disguise RenderStream).

1. Copy the OCIO config file from RenderStream Projects/<UEProject>/Content/<OcioConfig>.ocio.
   • See: OCIO Config file.
2. Place the copied config file into the following directory:
   • d3_projects/<PROJECT_DIR>/objects/ocio/.

Copied OCIO Config File

Apply OCIO settings in Designer

1. Open Project Settings….
2. Set Colour management to OCIO.
3. Set OCIO config using the OCIO config file used for the Unreal Engine project.

Selecting OCIO Config File

Set Input Transform on RenderStream Layer

Ensure the Input transform of the RenderStream layer matches the Transform Destination of Unreal Engine Plugins | Disguise RenderStream.

1. Open the RenderStream layer widget.
2. Right-click the Asset.
3. Set the Input transform to match the Transform Destination from Unreal.

Input Transform of RenderStream Layer

Verifying Colour with a Colour Checker

It’s a good idea to scientifically validate the colour pipeline using a colour checker. This section will guide you through setting up the pipeline to validate the colour accuracy of your rendering using a colour checker.

Designer provides a Colour Inspector tool to inspect the pixel values of the final output, ensuring colour accuracy.

Colour Checker Setup

We’ll use a colour checker from Color-Nuke GitHub. Select the .exr file based on your Working Color Space of Unreal Engine.

Working Color Space	Link
Rec.709	sRGB_ColorChecker2005.exr - Color-Nuke GitHub
ACES AP1 / ACEScg	ACEScg_ColorChecker2005.exr - Color-Nuke GitHub

Place the downloaded file in the Unreal Engine Content folder:

• RenderStream Projects/<UEProject>/Content

Color Nuke - sRGB Colour Checker

sRGB Colour Checker in Content Folder

Creating a Material in Unreal Engine

Once the colour checker is added as a texture, follow these steps to create a material:

1. Right-click the texture in the Content Drawer.
2. Select Create Material.

Create Material from Colour Checker Texture

Set colour space of texture (Optional)

If the colour space of the texture is different from your Working Color Space, adjust it:

• Double-click the texture.
• Under Texture > Source Color Settings, set the Color Space accordingly.
  • sRGB / Rec.709 for sRGB
  • ACES AP1 / ACEScg for ACEScg

Color Space of Colour Checker Texture

Configure the Material

To avoid lighting effects impacting the colour checker, you need to configure the material to be Unlit:

1. Double click the material created from the colour checker texture.
2. Set the Shading Model to Unlit.
3. Connect the RGB node of the Texture Sample to the Emissive Color input.

Colour Checker Material Settings

Viewport for Colour Checker

To create a viewport fully filled with the colour checker, it is recommended to add a dedicated Plane and CameraActor pair. While it is possible to use an existing CameraActor and Plane, using a dedicated pair ensures better control over the colour checker output.

1. Add a Plane and a CameraActor (Optional).

Plane and Camera Actor

2. Adjust the Transform of both actors.
   • See: Recommended Transform settings.
3. Select the Plane and open the Details panel.
4. Expand the Materials section.
5. Under Element 0, assign the created colour checker material to the Plane.

Setup Plane Material

6. Select the CameraActor.
7. Verify that the viewport is fully filled with the colour checker.

CameraActor Result Viewport

Warning

Ensure you have followed the instructions in Camera Actor Settings to prevent any unintended post-processing effects.

Recommended Transform to achieve the colour checker viewport

Actor	Location	Rotation	Scale
Plane	0.0, 0.0, 300.0	90.0, 0.0, 90.0	8.0, 4.5, 1.0
CameraActor	-400.0, 0.0, 300.0	0.0, 0.0, 0.0	1.0, 1.0, 1.0

Designer Colour Inspector

Note

Before proceeding, ensure that Designer RenderStream has been properly configured with OCIO (See: OCIO settings in Designer).

The Designer Colour Inspector tool allows you to inspect colour values at different stages of rendering. Since we are working with a RenderStream layer, follow these steps to use the Colour Inspector for the RenderStream layer:

1. Start the RenderStream workload.
2. Open the RenderStream layer widget.
3. Expand the Default.
4. Select Colour Inspector.
5. Change the Colour Space to Custom.
6. Set the Colour Space to sRGB - Texture:
   • Use sRGB - Texture for any type of colour checker (i.e. ACEScg).
7. Click on any pixel within the colour checker texture to view its value.
   • You can adjust the Number Format if needed.

Colour Inspector

8. Compare the pixel values with the Manufacturer’s sRGB color values from Wikipedia:
   • https://en.wikipedia.org/wiki/ColorChecker

####Natural Colours

Dark skin	Light skin	Blue sky	Foliage	Blue flower	Bluish green
#735244	#c29682	#627a9d	#576c43	#8580b1	#67bdaa
0.450980 0.321569 0.266667	0.760784 0.588235 0.509804	0.384314 0.478431 0.615686	0.341176 0.423529 0.262745	0.521569 0.501961 0.694118	0.403922 0.741176 0.666667

####Miscellaneous Colours

Orange	Purplish blue	Moderate red	Purple	Yellow green	Orange yellow
#d67e2c	#505ba6	#c15a63	#5e3c6c	#9dbc40	#e0a32e
0.839216 0.494118 0.172549	0.313725 0.356863 0.650980	0.756863 0.352941 0.388235	0.368627 0.235294 0.423529	0.615686 0.737255 0.250980	0.878431 0.639216 0.180392

####Primary and Secondary Colours

Blue	Green	Red	Yellow	Magenta	Cyan
#383d96	#469449	#af363c	#e7c71f	#bb5695	#0885a1
0.219608 0.239216 0.588235	0.274510 0.580392 0.286275	0.686275 0.211765 0.235294	0.905882 0.780392 0.121569	0.733333 0.337255 0.584314	0.031373 0.521569 0.631373

####Grayscale Colours

White	Neutral 8	Neutral 6.5	Neutral 5	Neutral 3.5	Black
#f3f3f3	#c8c8c8	#a0a0a0	#7a7a7a	#555555	#343434
0.952941 0.952941 0.952941	0.784314 0.784314 0.784314	0.627451 0.627451 0.627451	0.478431 0.478431 0.478431	0.333333 0.333333 0.333333	0.203922 0.203922 0.203922