Lumen Global Illumination and Reflections
- Fully dynamic GI and reflections for next-gen consoles; default system; "diffuse interreflection with infinite bounces and indirect specular reflections"; millimeters to kilometers.
- New projects enabled by default; UE4-converted projects not. Requires Generate Mesh Distance Fields (Software RT).
- "Lumen Global Illumination replaces Distance Field Ambient Occlusion (DFAO). Lumen Reflections replace Screen Space Reflections." Precomputed static lighting disabled, lightmaps hidden.
- GI: color bleed, indirect shadowing, infinite diffuse bounces; "full-resolution shading, while computing indirect lighting at a much lower resolution". Sky lighting in Final Gather incl. sky shadowing. Lower-quality GI for lit translucency and volumetric fog. Emissive propagates with no extra cost, but small bright emissive causes noise.
- Reflections: full roughness range; clear coat; glossy on translucency; High Quality Translucency Reflections; single layer water.
- All light types; Static mobility lights not supported.
- Settings: Use Hardware Ray Tracing when available ("significant scene update costs for scenes with more than 100,000 instances"); Ray Lighting Mode (Surface Cache default vs Hit Lighting for Reflections); Software Ray Tracing Mode (Detail vs Global Tracing); Generate Mesh Distance Fields (build time, memory, disk).
- Post process: Scene Lighting Quality, Scene Detail, Scene View Distance, Final Gather Quality, Screen Traces, Max Trace Distance ("Values that are too small cause lighting to leak into large areas, such as caves"), update speeds, Diffuse Color Boost, Skylight Leaking, Max Roughness To Trace, Max Reflection Bounces.
- "While local lighting changes propagate quickly, global lighting changes, like disabling the Sun, can take multiple seconds to propagate."
- Lumen Reflections can be used with baked static lighting (requires HWRT).
- Clear coat: single reflection ray per pixel; bottom layer assumed rough.