UE_Dynamic Lighting

1. Basic Lighting Concepts

• Direct Lighting
  Light that reaches a surface directly without any interference, providing clear and accurate illumination.
• Indirect (Bounced) Lighting
  Light that reflects off surrounding surfaces, contributing to mood, realism, and overall light intensity.
• Shadows
  Created by projecting geometry from the light’s point of view, helping define depth and spatial hierarchy.

2. Static vs Dynamic Lighting

• Static (Baked) Lighting
  Precomputed using Lightmass, offering high-quality lighting with minimal performance cost, but cannot be changed at runtime.
• Dynamic (Real-Time) Lighting
  Updated every frame, fully adjustable and animatable, but more performance-intensive.
• Ray Tracing
  Provides real-time global illumination and reflections, but requires high-end GPU hardware.
• Unreal Engine supports a hybrid workflow, with Lumen as the default lighting solution in UE5.

3. Light Types and Mobility

Light Types

• Directional Light
• Point Light
• Spot Light
• Rect Light
• Sky Light / HDRI
• Sun & Sky Blueprint

Light Mobility

• Static – Fully baked lighting, lowest performance cost
• Stationary – Baked indirect lighting with high-quality direct lighting (limited overlapping lights)
• Movable – Fully dynamic lighting and shadows, highest performance cost

4. Artificial Lighting – Practical Use

• Point Lights
  Physically accurate but expensive; shadow softness must be carefully controlled to avoid noise.
• Spot Lights
  Cost-effective and directional, suitable for theatrical and interior lighting.
• Rect Lights
  Very realistic but expensive; ideal for simulating screens, windows, and soft fill lights.
• Emissive Materials
  Can emit light in Lumen, but small emissive surfaces often produce noisy results and should not replace real light sources.

5. Reflection System

• Unreal Engine 5 uses Lumen Reflections by default.
• Reflection types include:
  • Screen Space Reflections (legacy)
  • Sphere and Box Reflection Captures (baked)
  • Planar Reflections
• Post Process Volume controls reflection intensity, quality, and roughness.
• Reflection captures mainly serve as baked solutions or fallback enhancements.

6. Lumen Overview

• Lumen is Unreal Engine 5’s fully dynamic global illumination and reflection system.
• Supports:
  • Infinite diffuse light bounces
  • Indirect specular reflections
  • Large-scale environments
• Deeply integrated with Nanite, enabling efficient high-detail lighting.
• Replaces older solutions such as SSGI, RTGI, and Skylight AO.

7. Lumen Setup and Quality Control

• Project Settings
  • Dynamic Global Illumination: Lumen
  • Reflection Method: Lumen
  • Enable Mesh Distance Fields
• Post Process Volume
  • Lumen Scene Quality
  • Lumen Scene Detail
  • Lumen View Distance
  • Final Gather Quality
• With supported hardware, Hardware Ray Tracing + Hit Lighting provides the highest-quality reflections.