Configure Unreal Engine applications to support passthrough with Hololight Stream

Objectives

  • Be able to configure your Unreal Engine application to work with passthrough on Hololight Stream.

  • Understand which settings need to be configured in which versions of Unreal Engine.

Configure Unreal Engine applications to support passthrough

If you enable passthrough and connect to an application made with Unreal Engine, passthrough may not work. To get passthrough to work, you must build the application with Unreal Engine version 5.5 or later. There are also some additional Unreal Engine-specific requirements depending on the version.

Passthrough with Unreal Engine requirements

Passthrough in applications made with Unreal Engine will only work if the following is true:

Unreal Engine passthrough support requirements
Version Requirement

All Unreal Engine versions

Enable "Alpha Output".

Unreal Engine 5.5

Enable "r.AlphaInvertPass".

Unreal Engine 5.6 and later

Enable "Invert scene alpha for passthrough".

Enable "Alpha Output"

Enable Project Settings > Rendering > Default Settings > Alpha Output.

unreal project settings rendering default settings

Configure "r.AlphaInvertPass"

Option A - Configure "r.AlphaInvertPass" using the console

  1. Open your Unreal Engine project.

  2. In the Output Log enter r.AlphaInvertPass 1.

Option B - Configure "r.AlphaInvertPass" using DefaultEngine.ini

  1. Open your Unreal Engine project.

  2. Go to Projects > <APPLICATION_NAME> > Config > DefaultEngine.ini.

  3. Edit DefaultEngine.ini and add:
    r.AlphaInvertPass=True
    under
    [SystemSettings]

    Add [SystemSettings] if it isn’t already there.

Enable "Invert scene alpha for passthrough"

Enable Project Settings > Plugins - OpenXR Settings > Passthrough > Invert scene alpha for passthrough.

unreal project settings plugins openxr settings passthrough invert scene alpha for passthrough