Right now, Unreal Engine 4 is lacking a completed global illumination system that works in real time.
- Volumetric Lightmap: Looks great but is static.
- Light Propagation Volume: Never completed and probably abandoned.
- Screen Space Global Illumination: Has limitations associated with screen space effects (such as lighting disappearing when it’s not on screen).
- Ray Traced Global Illumination: Visuals and performance are currently not viable for anything real time with consumer grade hardware.
- Voxel Global Illumination: Requires a separate branch of the engine (plus performance limitations, if I remember correctly).
Gaijin Entertainment has created their own real-time global illumination technique for their upcoming game, Enlisted. I feel that a feature like this could help fill a niche in UE4, especially for large open world games where users want high quality lighting features, but also want to use dynamic lights (for day/night cycles, avoiding baking, etc.).
On a side note, is anyone aware of any real-time GI features in the works for UE4 at the moment?