Global Illumination (Hybrid SDF GI)

XFSDK Light includes the Hybrid SDF GI implementation also used by XFSDK Core and the upcoming standalone GI plugin. This page covers Light-specific integration; the shared technical reference documents probe volumes, baking, update modes, quality, final gather, and limitations. Core and standalone GI use x_; Light uses xl_ with the same GI CVar suffixes.

Video: Setup

Configuration

[/Script/Engine.RendererSettings]
r.DynamicGlobalIlluminationMethod=3
r.GenerateMeshDistanceFields=True

[SystemSettings]
xl_gi_method=2

xl_gi_method	Method
0	Off (default)
1	Hybrid RT GI: reserved for the planned hardware ray tracing version
2	Hybrid SDF GI

r.DynamicGlobalIlluminationMethod=3 (Plugin) tells Unreal to hand indirect lighting to XFSDK Light. Without it the engine never calls the GI.

Quick start

1. Set the config above and restart the editor (distance fields need to build).
2. Place an XFSDK GI Volume actor (Place Actors panel, search "XFSDK GI Volume") and scale its box over the playable area. Use several volumes for large or multi-room levels.
3. Look around: probes converge over a few seconds. Use xl_gi_dfgi_lite_visualize 3 to see them.
4. Optionally press Bake GI on the volume to freeze it. See Baking.

Sky Light

Keep a Sky Light in the level. Its lighting feeds the GI's sky rays and lights pixels outside every volume. If the image looks noisy with the final gather on, check the Sky Light's distance-field shadowing first: in testing it was the main source of noise, not the GI.

Technical reference

The following behavior is shared with Core. The technical reference uses x_ commands; substitute xl_ for Light. Keep the rest of each shared GI CVar name unchanged.

• How it works
• GI volumes and update modes
• Baking
• Quality
• Final gather
• Settings and debugging
• Limitations
• Light console variables

Runtime API

XFSDK Light exposes the same GI mode-selection API as XFSDK Core. The functions can enable Hybrid SDF GI, switch to Unreal Engine Lumen Lite, disable dynamic GI, and query the active mode.

See Runtime GI API for the complete Blueprint and C++ function reference.

For XFSDK Light C++ projects, use:

• Module: XFSDK_System
• Header: XFSDK_GI_API.h
• Class: UXFSDKGIAPI
• Mode enum: EXFSDKGIMode