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Global Illumination

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Type
  • Class
Resource
  • urn:ngm:class:global-illumination
Domain
  • spatial-computing
Status
  • stable
Maturity
  • emerging
Quality
  • 0.72
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  • by: process:vault-migrate/1.0 · at: 2026-09-22T12:41:39.024503178Z
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  • urn:visionflow:page:9dc3956d24e6d09bc4f19b1fb3dbeb70d3270dea0a553ab76affb16ab6ff9c97
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Global Illumination (GI) is a rendering approach that simulates all light interactions within a scene, including both direct illumination from light sources and indirect illumination from light bouncing between surfaces. Techniques range from offline radiosity and photon mapping to real-time approximations such as voxel cone tracing, screen-space ambient occlusion, and hardware-accelerated ray tracing, producing physically plausible colour bleeding, soft shadows, and caustics.

Semantic Classification

Content

Key Characteristics

  • Indirect Lighting: Light bouncing between surfaces

  • Color Bleeding: Surface colors affecting nearby objects

  • Ambient Occlusion: Soft shadows in crevices and corners

  • Energy Conservation: Physical light intensity preservation

  • Scene-Wide Effects: Lighting influenced by entire environment

    Global Illumination Components

    Direct Illumination

  • Light arriving directly from sources

  • Shadows cast by occluding objects

  • Specular highlights and reflections

    Indirect Illumination

  • Diffuse Interreflection: Light bouncing between diffuse surfaces

  • Caustics: Focused light through reflective/refractive surfaces

  • Subsurface Scattering: Light penetrating translucent materials

  • Color Bleeding: Colored surfaces tinting nearby objects

    Techniques for Global Illumination

    Offline/Pre-computed Methods

    Radiosity

  • Solves form-factor equations between surface patches

  • View-independent, pre-computed solutions

  • Excellent for diffuse surfaces, struggles with specular

    Lightmapping/Baking

  • Pre-render lighting into textures

  • Fast runtime performance

  • Static lighting only, large memory footprint

    Photon Mapping

  • Emit photons from light sources, trace bounces

  • Store photon hits in spatial data structure

  • Query photon map during final rendering

    Real-Time Approximations

    Screen Space Ambient Occlusion (SSAO)

  • Approximate ambient occlusion from depth buffer

  • Fast, screen-space technique

  • Limited accuracy, no indirect lighting

    Voxel Cone Tracing

  • Voxelize scene geometry

  • Trace cones through voxel grid for indirect lighting

  • Balances quality and performance

    Light Propagation Volumes (LPV)

  • Inject direct light into 3D grid

  • Propagate light through grid iteratively

  • Fast approximation of one-bounce indirect light

    Real-Time Ray Tracing

  • Monte Carlo path tracing with denoising

  • Hardware-accelerated (RTX, RDNA)

  • High quality but demanding hardware

    Hybrid Approaches

  • Combine lightmapping with dynamic lights

  • Use SSAO/SSGI for dynamic indirect lighting

  • Selective ray tracing for important effects

    Definition

    Comprehensive lighting simulation that accounts for all light interactions in a scene, including direct illumination from light sources and indirect illumination from light bouncing between surfaces, producing photorealistic lighting with color bleeding, soft shadows, and ambient effects.

  • Ray Tracing

  • Rasterization

  • Physically-Based Rendering

  • Compute Shader

  • Light Probe

    Applications

  • Photorealistic metaverse environments

  • Architectural visualization in VR

  • Virtual film production stages

  • High-end virtual showrooms

  • Training simulations requiring realism

    Advantages

  • Photorealistic lighting quality

  • Natural ambient lighting

  • Color bleeding and subtle tinting

  • Unified lighting solution

  • Physically plausible results

    Limitations

  • Computationally expensive

  • Complex to implement and optimize

  • Memory intensive (lightmaps, probes)

  • Static scenes for pre-computed methods

  • Real-time methods require powerful hardware

    Performance Considerations

  • Pre-computation Trade-offs: Memory vs. runtime cost

  • LOD Integration: Simplify GI for distant objects

  • Probe Placement: Strategic light probe positioning

  • Update Frequency: Balance between quality and FPS

  • Denoising: Reduce samples via filtering/AI

    Metaverse Implementation Strategies

  • Use lightmapping for static architecture

  • Dynamic objects with light probes

  • SSAO/SSGI for low-end devices

  • Scalable quality settings (low to ultra)

  • Selective ray tracing on capable hardware

    References

  • Dutré, P. et al. (2006). Advanced Global Illumination, 2nd ed.

  • Ritschel, T. et al. (2012). “The State of the Art in Interactive Global Illumination”

  • Karis, B. (2013). “Real Shading in Unreal Engine 4”

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