Refining Lumen Reflections Quality

Tweak the reflection quality settings to achieve accurate, high-fidelity real-time reflections on metallic and rough surfaces.

In this lesson, you will learn how to fine-tune project and console settings to achieve high-fidelity Lumen reflections that remain stable and accurate across both polished metallic surfaces and rough, light-scattering materials.

Understanding the Reflection Pipeline

Lumen reflections primarily rely on the Surface Cache to capture lighting data from the scene. When you notice "splotchy" or low-resolution reflections, it is often because the Surface Cache is struggling to resolve fine detail in the distance or on complex geometry.

To push beyond the default quality, we focus on the Lumen Scene Quality and Reflection Quality multipliers. These are controlled via the r.Lumen.Reflections console variables.

Tuning Reflection Quality

If your metallic surfaces look noisy or lack sharpness, you can increase the quality of the ray-traced reflections. Access your ConsoleVariables.ini file or use the ~ console during runtime to adjust the following:

r.Lumen.Reflections.MaxRoughnessToTrace 0.6
r.Lumen.Reflections.DownsampleFactor 1
r.Lumen.Reflections.RayTracing.Refinement 1

MaxRoughnessToTrace: Increasing this value allows rougher materials to calculate reflections rather than falling back to low-quality screen-space cubemaps.
DownsampleFactor: Setting this to 1 forces the renderer to calculate reflections at full resolution rather than downsampled, significantly cleaning up the edges of reflections on metallic objects.
RayTracing.Refinement: This setting improves the denoising pass, which is essential for preventing the "swimming" or temporal noise often seen on reflective surfaces when the camera moves.

Balancing Roughness and Detail

When dealing with rough surfaces, Lumen uses Surface Cache data instead of hardware ray tracing. If these surfaces appear disconnected from the environment, increase the Lumen Scene Lighting Quality in the Post Process Volume. By setting this to a value of 2.0 or higher, you force the Surface Cache to capture more texel data, providing a much more accurate "base" for rough-surface reflections. Always monitor your GPU performance in the GPU Visualizer after making these adjustments, as high-fidelity reflections are one of the most expensive operations in the Lumen pipeline.

Key Takeaway: To achieve high-fidelity reflections, increase the Lumen reflection downsample factor to 1 and adjust the max roughness threshold to ensure accurate ray-traced feedback on both metallic and semi-rough surfaces.