Unreal Engine 5: Disabling Lumen for High FPS via Scalability.ini

The primary goal for this optimization is Systemic Bypass. Simply setting “Global Illumination” to Low in the in-game menu often leaves certain Lumen sub-systems running in the background. A custom Scalability.ini forces the engine to use Screen Space Global Illumination (SSGI) or simple Ambient Occlusion instead of heavy ray-traced bounces.

File Path

You must create or edit this file in your project’s (or packaged game’s) local configuration folder:

%LocalAppData%\[ProjectName]\Saved\Config\WindowsNoEditor\Scalability.ini

(Note: For some 2026 titles, the folder may be named Windows or WinGDK.)

Technical Configuration (The 2026 “Pure-Raster” Template)

Paste the following block into your Scalability.ini. This configuration specifically targets the sg.GlobalIlluminationQuality and sg.ReflectionQuality groups to ensure Lumen is 100% disabled at lower settings.

[GlobalIlluminationQuality@0]
r.Lumen.DiffuseIndirect.Allow=0
r.DynamicGlobalIlluminationMethod=0
r.Lumen.ScreenProbeGather.AdaptiveDirectLighting=0
r.SSGI.Enable=1

[ReflectionQuality@0]
r.Lumen.Reflections.Allow=0
r.ReflectionMethod=1
r.SSR.Quality=2
r.Lumen.Reflections.ScreenTraces=0

[PostProcessQuality@0]
r.Lumen.Reflections.Temporal=0
r.ScreenPercentage=100

Parameter Breakdown:

• r.Lumen.DiffuseIndirect.Allow=0: This is the “Kill Switch.” It completely disables the diffuse light bouncing that defines Lumen.
• r.DynamicGlobalIlluminationMethod=0: Forces the engine to “None.” This stops the GPU from calculating the Lumen scene, saving massive amounts of VRAM.
• r.ReflectionMethod=1: Switches reflections from Lumen to Screen Space Reflections (SSR). SSR only reflects what is on your screen, which is significantly cheaper than tracing the entire 3D scene.
• r.SSGI.Enable=1: Since we disabled the “fancy” lighting, we enable Screen Space Global Illumination. It provides a “fake” bounce light effect that looks 80% as good as Lumen for about 10% of the cost.

Strategy for 2026 FPS Dominance

• The “Low vs. Medium” Logic: In the template above, we used @0 (Low). If you want these changes to apply to the “Medium” setting, change the header to [GlobalIlluminationQuality@1].
• Virtual Shadow Maps (VSM): If you disable Lumen but your FPS is still low, the culprit is likely VSM. Add r.Shadow.Virtual.Enable=0 to your Scalability.ini under [ShadowQuality@0] to revert to traditional (and faster) Shadow Maps.
• Hardware Ray Tracing: Ensure r.Lumen.HardwareRayTracing=0 is set if you are on an older card. Even if Lumen is “off,” some games try to keep the Ray Tracing structures updated in the background, causing unnecessary CPU lag.
• Denoising Artifacts: When you disable Lumen, you might notice “noise” or “shimmering” on metallic surfaces. This is caused by the fallback SSR. To fix this, increase r.SSR.Quality=3 or set r.SSR.MaxRoughness=0.6 to limit where reflections appear.

Key Performance Comparison

Feature	Lumen (Default)	Scalability Fix (Raster)	FPS Gain (Estimated)
Global Illumination	Ray-Traced / Software	SSGI / Off	+15 – 30 FPS
Reflections	Full Scene Trace	Screen Space (SSR)	+10 – 20 FPS
VRAM Usage	High (Lumen Scene)	Low (Buffer Only)	~1.5GB Saved
Input Latency	Higher (Processing)	Minimal	Improved

Frequently Asked Questions (FAQ)

Conclusion and Expected Results

By overriding the GlobalIlluminationQuality and ReflectionQuality in your Scalability.ini, you are stripping away the heaviest parts of the Unreal Engine 5 pipeline. You can expect a significant jump in FPS stability, cooler GPU temperatures, and a much more responsive feel in fast-paced titles.