Lighting

Lighting in 3D graphics encompasses the full range of techniques that determine how light interacts with virtual scenes — from direct illumination (light sources hitting surfaces) to global illumination (light bouncing between surfaces), and from pre-computed (baked) solutions to fully dynamic real-time computation. Lighting is arguably the single most important factor in visual quality: the same geometry and textures can look flat or photorealistic depending entirely on how they're lit.

The fundamental categories of lighting in real-time graphics include direct lighting (rays from light sources to surfaces), indirect lighting (light that has bounced at least once off another surface), ambient lighting (a baseline fill that approximates environmental light), and emissive lighting (surfaces that emit their own light). Real-world lighting involves infinite bounces; real-time graphics must approximate this with finite computation.

Historically, game developers chose between baked and dynamic approaches. Baked lighting precomputes light transport into lightmaps — textures that store lighting information — delivering beautiful results for static scenes but unable to respond to moving objects or time-of-day changes. Dynamic lighting computes everything at runtime, enabling full interactivity but at higher computational cost. Modern engines increasingly blend both: Unreal Engine 5's Lumen provides real-time global illumination using a hybrid of screen-space traces, software ray tracing, and hardware ray tracing, allowing fully dynamic lighting at quality levels that previously required offline rendering.

The AI revolution is reshaping lighting. Neural radiance caching uses trained networks to predict indirect lighting, dramatically reducing the rays needed for quality results. Differentiable rendering enables optimization of lighting parameters through gradient descent. Neural rendering approaches can learn lighting models from real-world photographs. As path tracing becomes feasible in real time through hardware acceleration and AI denoising, the gap between offline and real-time lighting quality continues to narrow.