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Installation

Install Spectral through Fab using the Epic Games Launcher, then enable it in the project. You do not need to download a ZIP or manually place a plugin folder.

1 Add Spectral to your Fab library​

Acquire Spectral on Fab using the Epic account you use in the launcher. You can do this through the Fab website or Unreal's Fab window. Acquiring the plugin adds it to your library; it does not install it into an engine automatically.

2 Install to Engine​

  1. Save your work and close Unreal Editor.
  2. Open Epic Games Launcher > Unreal Engine > Library.
  3. Find Spectral in Fab Library. Refresh the library if a recent purchase is not listed.
  4. Choose Install to Engine, select the supported engine version used by your project, and start the installation.
  5. Wait for the download and installation to finish.

The engine selector only offers installed versions that the plugin supports. If your version is missing, check the supported versions on the Fab listing and your installed engine versions. Do not copy binaries from another engine version. See Epic's plugin installation guide.

One installed copyNote

If you previously installed Spectral manually, back up that installation and resolve the duplicate before using the Fab-installed copy. A project-level copy can conflict with the engine-installed version. Fresh Fab installations do not require a project Plugins folder.

3 Enable it in your project​

  1. Open your project with the engine version you selected in the launcher.
  2. Open Edit > Plugins, search for Spectral, and enable it.
  3. Restart when prompted.

Do not enable the separate GPU Lightmass plugin alongside Spectral. Spectral supplies its own baker.

Checkpoint: Spectral is enabled and its panel opens from the editor toolbar. This confirms the plugin is loaded, not that the project is ready to bake.

4 Configure rendering and shader hooks​

  1. Open the Spectral panel and select Settings.
  2. Review required project settings, then use Fix Settings to apply the required group.
  3. Review Fix Suggested Settings separately. It can change other renderer features and light settings, so do not apply it blindly to an existing project.
  4. Click Enable Shader Hooks. Read the result and resolve any reported error.
  5. Save changes, restart the editor when requested, and wait for shader compilation to finish.

For baking, also select the supported Windows, DirectX 12, SM6 authoring configuration with hardware ray tracing available. Fab installation does not configure the project's active graphics API or provide missing GPU support. Follow First bake for the full preparation sequence.

Shader hooks affect the engine installationWarning

Close other editor instances using this engine before changing hooks. These modifications are shared by projects using that installation, not isolated to the current project. If the engine directory is not writable, resolve the reported permission problem rather than copying shader files by hand.

Checkpoint: Settings reports the required values and enabled shader hooks after the restart. Allow compilation to finish before judging missing lighting or material errors.

Update Spectral through the launcher​

Save a recoverable project version and close editor instances using the engine. In the launcher, open Unreal Engine > Library, find the engine tile, and use Installed Plugins to check for and apply an available Spectral update. Keep installation and removal under the launcher's management.

Reopen the project and check Spectral > Settings. Use Update Shader Hooks when offered, restart, and let shaders compile. If a probe volume reports Rebake Needed, rebuild its lighting.

After updating Unreal itself, install Spectral for that engine version through Fab as well. Do not assume an installation for one engine tile also installs it for another.

Remove Spectral​

  1. While Spectral is still enabled, use Settings > Disable Shader Hooks.
  2. Confirm restoration succeeded. If it reports missing backups or another error, resolve that first.
  3. Save your work and close Unreal Editor.
  4. In the launcher, open the engine tile's Installed Plugins and remove Spectral.

Removing an engine plugin affects projects using that installation. Keep project backups and review dependencies on Spectral actors, components, and materials before opening those projects without it. Epic documents launcher-managed removal in Install Unreal Engine.

For hook status and failure messages, see Shader hooks.