Lumen
Lumen: Dynamic GI & Reflections
Section titled “Lumen: Dynamic GI & Reflections”- Lumen Core Features
- Default UE5 GI/reflection system
- “Not dependent on machine” unlike raytracing
Good GPU helps maximize capabilities
- Technical Capabilities
- Diffuse Features
Infinite light bounces Color bleeds Works with nanite geometry
- Sky Handling
Part of final gather process Creates darker indoor spaces “More natural lighting effect”
- Material Support
Lit translucency Volumetric fog Emissive materials at no extra cost
- Size/brightness limits exist
Clear coat materials
- Reflection Comparison
- Screen Space Reflections
Only reflects visible viewport Objects out of frame disappear “Cheaper alternative to lumen”
- Lumen Reflections
Maintains off-screen objects Full material roughness range Shows diffuse GI in reflections
- Global Illumination
- Screen Space GI
Loses indirect light off-screen Limited bounces
- Lumen GI
Maintains off-screen lighting Infinite bounces possible “Best results for real-time”
- Debug Tip
- Show modified properties via gear icon
Helps track changed settings Useful for inherited work
Lumen revolutionizes UE5’s lighting by providing real-time GI and reflections without hardware dependencies. Unlike screen space alternatives, it maintains consistent lighting and reflections regardless of viewport visibility.
Lumen Setup & Optimization
Section titled “Lumen Setup & Optimization”- Required Setup
- Distance fields must be enabled
- Replaces:
Screen space reflections Screen space GI Distance field ambient occlusion
- Project Settings
- Rendering > Global Illumination
Set GI method to Lumen Reflection method to Lumen “Reflection capture resolution: 2048”
- Hardware Ray Tracing
Requires RTX card Change ray lighting to “hit lighting reflections” Enable high quality translucency
- Additional Requirements
Enable Shader Model 6 Disable static lighting Turn off ambient occlusion baked lighting Enable virtual shadow maps
- Works with Nanite
- High efficiency culling
- Post Process Volume Controls
- Access via Create > Visual Effects
- Key Settings:
Infinite unbound for global effect Manual exposure control Lumen specific:
- Scene lighting quality
- Scene detail
- View distance
- Final gather quality
- Trace distance
- Limitations & Performance
- Higher values increase GPU load
Scene detail affects noise “Max 8 reflection bounces”
- Material Considerations
Emissive lights increase noise Reflective materials need balance “Trade-off between visual fidelity and performance”
Lumen provides advanced real-time lighting but requires careful setup and optimization. Success depends on balancing quality settings with performance requirements based on project needs and hardware capabilities.