UnrealLink
UnrealLink is under active development, so it might change in the future.
UnrealLink is a window in LightAct where you can set up most of LightAct's integration with Unreal Engine. So let's describe every section of this window one by one.

UE Editor path

  • UE Editor path: this is where you set up the path to UE4Editor.exe or UE5Editor.exe.
Choosing the UEEditor path also determines which version of Unreal Engine LightAct is going to launch when launching .uproject Unreal assets.

Sync

  • Send timecode to UE: this enables or disables sending of LightAct's TC to Unreal.
  • Lock UE to dropdown determines whether you want to enable Genlocking of Unreal to LightAct and if yes, whether it should be to every LightAct's frame or every second, every third etc. In most cases, you'll want to enable Every frame.
Good to know: If Unreal Engine cannot keep up with LightAct's framerate, you might want to lower LightAct's FPS in Project Settings.
  • Wait for UE texture: this checkbox enables/disables LightAct's sub-frame latency feature.

nDisplay Settings

LightAct's management of nDisplay follows these steps:
  1. 1.
    import some Unreal Assets,
  2. 2.
    create an .ndisplay configuration file,
  3. 3.
    generate launch command,
  4. 4.
    launch nDisplay,
  5. 5.
    kill nDisplay (optional).

Importing Unreal Assets

To use UnrealLink you need at least one Unreal asset. Unreal asset can be either an executable of a packaged game or, more commonly, a .uproject file of Unreal Engine project.
To import an Unreal Asset, simply drag .exe or .uproject file into LightAct's window.
Once you've imported them, they will appear as radio buttons in UnrealLink window. Select one of them before proceeding.

Creating an .nDisplay configuration file

nDisplay Throwers or Projectors

To create an .ndisplay config file you need to have at least one thrower or project in the Viewport which has nDisplay checkbox enabled. This means it will get used as a template for nDisplay viewport.

Creating .ndisplay file

Click on ... button and select or create an .ndisplay file.
Don't forget to click on Generate config file button in order to generate it.

Launching nDisplay

The simple way to launch nDisplay is to click on Generate command button.
After this, the command will appear in the textbox below.
Then, you can click on Launch nDisplay button.
If you have enabled Every frame in the Lock UE to dropdown, then a few seconds after you've clicked on Launch nDisplay button, you will see real-time stats of Unreal Engine instance.
The stats won't appear if you haven't installed, enabled and set up LightAct plugin correctly.

Additional arguments and console commands

​There are 2 textboxes above the Generate command button:
  • Exec cmd line Args: this adds additional command line arguments to the launch command. For example, if you add -trace , Unreal Engine instance will immediately try to connect to UnrealInsights tool.
  • Custom ExecCmds: this passes additional console commands

Advanced settings

If you enable Show advanced settings, you can adjust additional settings of your nDisplay instance. A lot of these are taken from Unreal's default settings, so we won't describe them in detail here.
More information on Unreal's nDisplay can be found in Unreal's User Documentation.
There are 2 textboxes above the Generate command button:
However, the ones we should explain in a bit more detail are:
  • Render offscreen: this prevents Unreal to create windows and instead renders the content off screen.
  • Enable mGPU: enable this if you use multiple GPUs and want some or all of the nDisplay viewports to render on a different GPU than the one LightAct is rendering on.
You need an NVidia card with NVLink to enable multiple GPU rendering with Unreal Engine.

Killing nDisplay

To kill an nDisplay instance, just press Kill nDisplay button.
nDisplay instances that were launched by LightAct are also killed when you exit LightAct