Lumen (Unreal Engine)

Lumen
Information
Type	Global illumination system
Industry	Real-time computer graphics
Developer	Epic Games
Operating System	Windows, Linux, macOS, Android
Supported Devices	PlayStation 5, Xbox Series S and X, Nintendo Switch 2, high-end PCs; Android with Vulkan (per the Unreal Engine 5.8 documentation)
Release Date	May 26, 2021 (Unreal Engine 5 Early Access); April 2022 (Unreal Engine 5.0)
Website	https://dev.epicgames.com/documentation/en-us/unreal-engine/lumen-global-illumination-and-reflections-in-unreal-engine

Lumen is the dynamic global illumination and reflections system in Unreal Engine 5, developed by Epic Games. Epic's documentation describes it as a system that "renders diffuse interreflection with infinite bounces and indirect specular reflections" in environments at scales "ranging from millimeters to kilometers." Lumen computes indirect lighting at run time, so Epic's examples of changing the angle of the sun, turning on a flashlight, opening an exterior door or blowing up a wall all update indirect lighting and reflections without baked lightmaps. It is enabled by default in new Unreal Engine 5 projects.

Epic first showed Lumen on May 13, 2020, in the "Lumen in the Land of Nanite" demo that revealed Unreal Engine 5 running on a PlayStation 5. It shipped to developers in the Unreal Engine 5 Early Access build of May 2021 and in the full engine release of April 2022, together with the Nanite virtualized geometry system.

For virtual reality development, Lumen's main constraints are its performance targets and renderer requirements. Epic designed it around console frame rates of 30 and 60 frames per second, and it does not work with the forward shading renderer that Epic recommends for VR projects. As of the Unreal Engine 5.8 documentation, Epic states that "Lumen does not currently support Virtual Reality (VR) systems" and classes Nanite and Lumen on XR as experimental and not officially supported, available only on PC with the deferred renderer and DirectX 12.

Reviewed 18 October 2026. Checked every date, number, quote and attribution against the cited Epic documentation (5.0-5.8 versioned pages and release notes), SIGGRAPH 2021/2022 course pages and notes, and the cited press articles. About review dates.

History

Reveal and early access

Epic revealed Unreal Engine 5 on May 13, 2020, with a real-time demo titled "Lumen in the Land of Nanite." The demo ran on PlayStation 5 development hardware. Road to VR reported that it ran at 2560x1440 and 30 frames per second. In Epic's description quoted by Road to VR, "Lumen is a fully dynamic global illumination solution that immediately reacts to scene and light changes," and it "erases the need to wait for lightmap bakes to finish and to author light map UVs." On the same day an Epic spokeswoman told UploadVR that Unreal Engine 5 would continue to support current VR headsets, naming PlayStation VR, Oculus Quest and PC VR devices.

Daniel Wright, an Engineering Fellow in graphics at Epic Games, is identified in his SIGGRAPH 2021 and 2022 speaker biographies as Technical Director of Lumen. He presented its final gather in the talk "Radiance Caching for Real-time Global Illumination" in the Advances in Real-Time Rendering in Games course at SIGGRAPH 2021, held online on August 11, 2021. The talk abstract says hardware ray tracing could "barely afford 1 ray per pixel for diffuse indirect," while global illumination needs "hundreds of effective samples for high quality indoor lighting."

Unreal Engine 5 entered Early Access on May 26, 2021, through the Epic Games Launcher and GitHub. Engadget wrote that Lumen "provides real-time lighting that adjusts for the time of day and clouds overhead," and Epic expected the full release in early 2022.

Unreal Engine 5.0

Epic released Unreal Engine 5 to all developers in April 2022. According to the 5.0 release notes, Lumen had gained these features since Early Access: a full hardware ray tracing pipeline for global illumination and reflections, Far Field hardware ray tracing for long view ranges, a feedback-driven Surface Cache, visualization view modes, translucency and radiosity final gathers, Landscape support, and support for the Subsurface and Two-Sided Foliage shading models. Epic also wrote that Lumen had "Shipped on next-gen consoles in The Matrix Awakens." The same notes said Lumen was not yet ready for in-camera VFX work with the VR and nDisplay rendering pipelines, and that Epic expected "to support nDisplay and VR workflows in the future."

In the Unreal Engine 5.0 documentation, software ray tracing required "DirectX 11 with support for Shader Model 5 (SM5)" and an NVIDIA GeForce GTX 1070 or better. That documentation also said Lumen did not support mobile platforms and that there were "no plans to develop a dynamic global illumination system for the mobile renderer." It listed scene captures and split-screen as unsupported.

At SIGGRAPH 2022, Wright and his Epic colleagues Krzysztof Narkowicz and Patrick Kelly gave a full technical talk in the Advances course, "Lumen: Real-time Global Illumination in Unreal Engine 5." It covered software ray tracing with signed distance fields, the virtualized surface cache, hardware ray tracing, final gathering and reflections, and the lighting of the procedural city in The Matrix Awakens.

Later versions

The table lists Lumen changes and platform notes that Epic's release notes and versioned documentation record for each later release.

Version	Lumen changes (per Epic's release notes and documentation)
5.1	More accurate foliage in software ray tracing; the High scalability level "targeted at 60fps on next generation consoles"; software ray tracing samples the Surface Cache directly; mirror reflections on translucent surfaces; Single Layer Water reflections; Lumen in Scene Captures (persistent memory "from 300 to 600 MB or more"); multiple nDisplay viewports; experimental hardware ray tracing on Vulkan; initial stereo support for Nanite, Lumen and Temporal Super Resolution on PC with the deferred renderer
5.2	Notes that hardware ray tracing for Lumen is not supported on macOS, so Lumen falls back to software ray tracing on Apple silicon Macs, with lower-quality results
5.3	Stereo improvements for Lumen global illumination: per-view caches are partly shared between the two eye views (console variable r.Lumen.StereoOptimizations)
5.4	"Lumen on Mobile (Experimental)": support on recent mobile devices using the desktop deferred renderer
5.5	Documentation now lists DirectX 12 with Shader Model 6 for software ray tracing (previously DirectX 11 with Shader Model 5) and states that hardware ray tracing "is enabled by default"
5.6	Hardware ray tracing optimizations that Epic says bring hardware ray tracing to "the frame budget of the software ray tracing mode"; fix for reflection artifacts in split screen
5.7	"Lumen HWRT path now supports split screen"; half-resolution screen probe integration on the High scalability level, which Epic says saves about 0.5 ms on console at 1080p
5.8	Lumen Lite (Beta), a medium-quality global illumination mode that Epic says is "twice as fast as Lumen high quality"; Screen Space Global Illumination deprecated as "superseded by Lumen GI"; removal of the deprecated r.Lumen.Supported.SM5 setting

Unreal Engine 5.8 was released on June 17, 2026, at Epic's State of Unreal event. Its release notes describe Lumen Lite as using "Irradiance Fields with Probe Occlusion" and as "the new default for current-generation handheld consoles, where it can be used at 60fps." It is also supported on PC. The detailed notes call the same path Lumen Medium Quality, "targeted at low end PC and handhelds." It uses an Irradiance Field Gather that reuses the World Space Radiance Cache, traces no reflection rays (smooth surfaces take reflections from Screen Space Reflections, rough ones from radiance probe mipmaps), and disables tracing against skeletal meshes. Guru3D reported Epic's claims that the feature offers up to twice the performance of the High preset and can run on Nintendo Switch 2 at a 60 frames per second target.

How it works

Ray tracing methods

Lumen has two ray tracing methods. Hardware ray tracing traces against triangles, supports skinned meshes, and can evaluate lighting at the hit point. It requires Windows 10 with DirectX 12 or Linux with Vulkan, and an NVIDIA RTX 2000 series or AMD RX 6000 series graphics card or newer; PlayStation 5, Xbox Series S and X, and Switch 2 also support it. Software ray tracing traces against signed distance fields and needs a DirectX 12 graphics card with Shader Model 6, NVIDIA GeForce GTX 1070 or better. If hardware ray tracing is unavailable, Lumen falls back to the software path.

In software mode, the engine merges per-mesh distance fields into a Global Distance Field. By default Lumen traces each mesh's own distance field for the first two meters of a ray and the Global Distance Field for the rest. The Lumen Scene used by software tracing covers 200 meters from the camera by default and up to 800 meters with the Lumen Scene View Distance setting. With hardware ray tracing, Far Field traces extend lighting to one kilometer by default when World Partition hierarchical level of detail is set up. Before either method, Lumen runs screen traces, which sample scene depth and color.

The SIGGRAPH 2022 course notes explain why Epic built a software path. Hardware ray tracing "is great and it is the future," the authors wrote, but they needed options to scale down to PC graphics cards without it and to 60 frames per second on consoles, and to handle heavily overlapping meshes. They first tried ray tracing captured heightfields ("cards"), which leaked light where coverage was missing, and settled on mesh signed distance fields for the start of each ray. For the merged, coarser scene representation used farther along a ray they tried runtime voxel cone tracing, which also leaked, before arriving at a Global Distance Field.

Surface Cache

A distance field hit gives only a position and a normal, with no material or lighting. Lumen solves this with the Surface Cache, an automatic parameterization of nearby surfaces built from "cards," which the course notes describe as projected, axis-aligned rectangular clusters of surfels placed on each mesh during import. Static meshes get 12 cards by default. Skeletal meshes get six cards around their bounds, so their coverage is limited when they deform. Areas without card coverage do not bounce light.

Final gather

The opaque final gather is built on screen space radiance caching. Lumen places probes on screen pixels, more densely where geometry is detailed, traces rays from them, and interpolates the result to other pixels on the same plane. The screen space radiance cache runs at 1/16 resolution in each dimension. A world space radiance cache handles distant lighting at lower resolution. On PlayStation 5 at 1080p, the course notes give a total Lumen cost of 2.77 ms on High settings (1/16 ray per pixel for the final gather) and 4.63 ms on Epic settings (1/4 ray per pixel) in the "Lumen in the Land of Nanite" demo, using software ray tracing with the Global Distance Field only.

Performance targets and limits

Epic's documentation gives Lumen's primary target as large open worlds at 60 frames per second on current consoles (the High scalability level) and its secondary target as indoor lighting at 30 frames per second (the Epic level). The Epic level costs about 8 ms for global illumination and reflections on these consoles at 1080p internal resolution, with Temporal Super Resolution upscaling toward 4K.

Lumen does not support PlayStation 4 or Xbox One. It cannot be combined with static lighting from lightmaps for global illumination, and it is "not compatible with Forward Shading." Software ray tracing works best with walls at least 10 cm thick and with modular level geometry, and it does not support World Position Offset. Global lighting changes such as turning off the sun "can take multiple seconds" to propagate.

Use in VR and AR

Launch status

At the Unreal Engine 5.0 launch, Epic told Road to VR: "we have no timeframe to share in terms of Lumen and Nanite support for VR experiences," adding that it was exploring how to bring them to more platforms. Ben Lang wrote that Lumen's 60 and 30 frames per second console targets were "a far cry from the 90 FPS minimum for most PC VR headsets," that stereo rendering adds cost, and that techniques such as single-pass stereo and foveated rendering might not yet work with Nanite and Lumen.

PC VR experiments

The 5.1 release notes added "initial stereo support for Nanite, Lumen and Temporal Super Resolution," limited to PC with the deferred renderer, and listed "Added Lumen hardware raytracing in VR" among the XR changes. Before the 5.1 release, UploadVR reported in September 2022 that Heavenue CEO Alex Coulombe had run Lumen and Nanite in VR with a 5.1 build at 90 frames per second, on a laptop with a mobile RTX 3080 streaming to a Quest headset over Air Link. The same report noted that Nanite and Lumen did not work on Android at the time, so native Quest 2 games were limited to older techniques. In October 2022 Road to VR covered a cave scene built on a 5.2 development branch and run on an NVIDIA RTX 3090, and wrote that the features "aren't yet fully optimized for VR." Unreal Engine 5.3 then reduced Lumen's stereo cost by sharing part of its per-view caches between the two eyes.

Current documentation

As of the Unreal Engine 5.8 documentation, two Epic pages describe Lumen's VR status:

• The Lumen technical details page says: "Lumen does not currently support Virtual Reality (VR) systems. While VR can be supported, the high frame rates and resolutions required by VR make dynamic global illumination a poor fit." The same sentences appear in the 5.0 documentation.
• The "Nanite and Lumen for XR" page says Nanite and Lumen on XR "are considered experimental and are not officially supported." They are "Only supported on PC with the Deferred Renderer and DX12" and "Not supported on Mobile XR hardware." Since 5.1 they render in both eye views, so "you might struggle to achieve your target frame rate even with top-of-the-line hardware."

Mobile support has changed separately from XR support. Unreal Engine 5.4 added experimental Lumen support on recent mobile devices using the desktop deferred renderer, and the 5.8 documentation says Lumen "is supported on Android Vulkan and can be used with the Mobile Renderer." The XR page still excludes mobile XR hardware.

Conflict with forward rendering

Epic's XR best practices page tells developers to enable forward shading, set the anti-aliasing method to multisample anti-aliasing (MSAA), and enable Instanced Stereo. It warns that screen space global illumination can create differences between the two eyes that cause discomfort, and that "VR apps using ray tracing currently aren't able to maintain the resolution and frame rate needed for a comfortable VR experience." Epic's forward shading page says forward rendering "provides a faster baseline" and "better anti-aliasing options than the Deferred Renderer." Since Lumen requires the deferred renderer, a VR project chooses between Lumen and the renderer Epic recommends for headsets.

Notable uses

Besides the 2020 PlayStation 5 reveal demo, Epic used Lumen in The Matrix Awakens demo, which the 5.0 release notes say shipped Lumen on current consoles. Fortnite Battle Royale Chapter 4 moved to Unreal Engine 5.1 in December 2022 and used Lumen for real-time global illumination at 60 frames per second and for reflections on glossy materials and water on PlayStation 5, Xbox Series X and S, PC and cloud gaming. Epic has also extended Lumen to virtual production pipelines: the 5.1 release added support for multiple nDisplay viewports, each with its own Lumen Scene.

See also

• Unreal Engine
• Nanite
• Ray tracing
• Forward rendering
• Stereoscopic rendering
• Instanced Stereo Rendering