Unreal Engine Lumen Setup: Lighting and Reflection Settings for Archviz

What will you learn in this guide?

This guide explains how to enable Lumen in Unreal Engine 5, configure the core lighting and reflection settings, and assess hardware ray tracing options. Lumen dynamically calculates light bouncing indirectly off surfaces and reflections. These features can help you evaluate color bleeding, shadows, and the appearance of reflective surfaces directly in the scene, especially in interiors.

This guide is based on information in Epic Games’ Unreal Engine documentation. The documentation does not specify a particular minor version or account requirement, so no specific version number or user account requirement should be assumed. Hardware ray tracing requires support from the graphics card, RHI, and operating system; verify the relevant settings on the target machine.

Requirements and initial checks

Lumen is enabled by default for global illumination and reflections in newly created projects. In projects converted from UE4 to UE5, however, Lumen is not enabled automatically. This behavior helps prevent changes to the existing lighting setup in older projects from occurring unexpectedly.

Before you begin, check the following:

• Determine whether the project was newly created or converted from UE4.

• If you plan to use hardware ray tracing, check that the graphics card, RHI, and operating system support it.

• If you’re using software ray tracing, account for the Generate Mesh Distance Fields requirement and its impact on build time, memory usage, and disk size.

• Make a note of the project’s static lighting setup. When Lumen is enabled, precomputed static lighting contributions are disabled and lightmaps are hidden.

Enabling Lumen and configuring it in the scene

1. Choose the global illumination method. Go to the Rendering section in Project Settings. Set the method under Dynamic Global Illumination to Lumen. This system calculates indirect light from surfaces and color bleeding between nearby surfaces.

2. Set the reflection method. In the same settings, set Reflection Method to Lumen in the Reflections category. Global illumination and reflections can be selected separately, so check that both are configured to suit the project. Lumen reflections work with different roughness values; reflections on translucent surfaces can also be produced at different quality levels, depending on the relevant options.

3. Check the mesh distance field requirement. Generate Mesh Distance Fields may be enabled when you turn on Lumen. This feature is required for Lumen’s Software Ray Tracing mode. The engine may prompt you to restart after enabling it. Keep in mind that generating mesh distance fields can increase build time, memory usage, and the disk size of static meshes.

4. Adjust quality with a Post Process Volume. Lumen’s artist-controlled settings are in the Global Illumination and Reflections categories of a Post Process Volume. Increasing Final Gather Quality can improve indirect lighting quality and reduce image noise, but it also increases GPU costs. Higher values for settings such as Lumen Scene Detail and Scene View Distance can help the scene represent smaller objects or extend lighting to greater distances. These settings also add GPU load.

5. Increase reflection quality based on measurements. The Quality setting in the Reflections section can improve reflections and reduce noise, but comes with a performance cost. For high-quality mirror reflections on translucent surfaces, the relevant project and Post Process Volume options must be enabled. This option can increase GPU costs.

6. Review light sources and emissive surfaces. Lumen supports Directional, Sky, Point, Spot, and Rect lights. Emissive materials can also contribute to light propagation, but very small, bright emissive areas can create image noise. Shadows soften as light sources get larger or the angle of a directional light widens; compare these changes across different parts of the scene.

Requirements for using hardware ray tracing

To use hardware ray tracing, enable Support Hardware Ray Tracing under Engine > Rendering > Hardware Ray Tracing in Project Settings. This feature requires Support Compute Skin Cache; you may see a warning about this option when enabling the project setting.

Enabling this support checkbox alone is not enough for Lumen to use hardware ray-traced reflections. You also need a compatible graphics card, RHI, and operating system; Use Hardware Ray Tracing when available must be enabled in the Lumen settings, and Ray Lighting Mode must be set to Hit Lighting for Reflections. In this mode, lighting is calculated where the ray hits the surface, which can improve reflection quality but significantly increases GPU costs. Surface Cache is the default method, used for better performance. If the hardware or system is not supported, Lumen may fall back to software ray tracing.

In dense scenes, be mindful of the cost of updating the scene with hardware ray tracing. According to Epic’s documentation, this cost can be significant in scenes with more than 100,000 instances. Test the same camera framing before increasing quality settings. Post Process Volumes let you use lower quality across a large area of the scene and higher reflection quality in a specific interior.

Considerations for architecture and archviz workflows

Architecture, interior design, and archviz teams can use Lumen to evaluate lighting and material changes dynamically. Reviewing daylight, indirect lighting, and reflective surfaces together in interiors provides visual feedback for design decisions. However, disabling static lighting contributions when switching a project to Lumen can change the appearance of scenes that rely on precomputed lighting. It’s important to compare the old and new settings in converted projects.

Test hardware compatibility and performance on the workstation that will be used for presentations or real-time walkthroughs. Don’t apply Hit Lighting for Reflections and high quality values automatically to every scene; consider the GPU budget and scene complexity together. For objects using Nanite, independent ray-traced shadows can be generated through Nanite Fallback Target. If a low-detail fallback mesh causes visual artifacts, options include disabling Nanite on the affected object or increasing the Fallback Target value.

Common issues and next steps

Don’t assume Lumen will be enabled automatically in a project converted from UE4 to UE5. Check both the Dynamic Global Illumination and Reflection Method settings. You may need to restart the engine after changing Generate Mesh Distance Fields; ignoring this requirement can prevent the new setting from taking effect.

Another common mistake is increasing several quality settings at once without measuring the result. Final Gather Quality, reflection quality, scene detail level, and ray tracing mode can each affect GPU costs in different ways. Keep the camera and lighting conditions the same, change one setting at a time, and compare the results in interior corners, on reflective surfaces, and in distant details.

As a next step, use Post Process Volume settings for different areas and test performance on the target computer. If you plan to use hardware ray tracing, verify Support Hardware Ray Tracing, Support Compute Skin Cache, Use Hardware Ray Tracing when available, and Hit Lighting for Reflections together. If the hardware is unsupported, account for software ray tracing and its mesh distance field requirement.

Sources and licensing

This guide has been adapted into Turkish based on information in Epic Games’ “Lumen Global Illumination and Reflections in Unreal Engine” and “Hardware Ray Tracing in Unreal Engine” documentation. The sources are freely accessible; as their text does not specify a particular open-content license, no additional license type is claimed.