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# Global illumination and baked lighting

Light scenes realistically by precomputing illumination so surfaces pick up bounced color and ambient detail without recalculating it every frame.

## Overview

This collection gathers the tools for adding precomputed and environment-based lighting to your scenes. Use it to choose how surfaces respond to light, to bake static illumination and capture indirect light that nearby objects can sample, and to generate the surrounding imagery that lights a scene and fills its background. Reach for these features when you want richer, more believable lighting than real-time computation alone provides, while keeping rendering efficient. They suit scenes with mostly fixed lighting, where investing in precomputation pays off in visual quality and performance.

## Topics

### Lighting models

[`enum LightingModel`](/documentation/RealityKit/LightingModel)

The lighting model used by a [`ShaderGraphMaterial.Program`](/documentation/RealityKit/ShaderGraphMaterial/Program-swift.struct).

[`struct LitLightingModel`](/documentation/RealityKit/LitLightingModel)

Configuration for RealityKit’s physically based lighting model.

[`struct UnlitLightingModel`](/documentation/RealityKit/UnlitLightingModel)

Configuration for an unlit lighting model, which renders without any light interaction.

[`struct HairLightingModel`](/documentation/RealityKit/HairLightingModel)

Configuration for RealityKit’s hair lighting model.

### Lightmaps and light probes

[`class LightmapResource`](/documentation/RealityKit/LightmapResource)

A resource containing references to lightmap texture atlases
and descriptions of how parts of the atlases map to meshes in
the scene.

[`struct LightmapComponent`](/documentation/RealityKit/LightmapComponent)

Describes how a lightmap is applied to parts of the scene.

[`class DiffuseProbeResource`](/documentation/RealityKit/DiffuseProbeResource)

A resource containing baked diffuse lighting data organized as a tetrahedral probe mesh.

[`struct DiffuseLightProbeGroupComponent`](/documentation/RealityKit/DiffuseLightProbeGroupComponent)

A component that stores diffuse probe data for a spatial region.

[`struct DiffuseLightProbeReceiverComponent`](/documentation/RealityKit/DiffuseLightProbeReceiverComponent)

A component that receives diffuse lighting from a referenced probe group.

### Environment texture generation

[`class ImageBasedLightTextureGenerator`](/documentation/RealityKit/ImageBasedLightTextureGenerator)

An object that generates image-based-lighting diffuse and specular cube
textures from a skybox.

[`class SkyboxGenerator`](/documentation/RealityKit/SkyboxGenerator)

An object that generates a skybox cube texture from an equirectangular source.

[`enum TextureSamplingQuality`](/documentation/RealityKit/TextureSamplingQuality)

A discrete trade-off between generation time and texture quality, used by
[`SkyboxGenerator`](/documentation/RealityKit/SkyboxGenerator) and [`ImageBasedLightTextureGenerator`](/documentation/RealityKit/ImageBasedLightTextureGenerator).


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