Performance tuning

If the sky system is too heavy, dial these knobs in order. Each step generally recovers more performance than the last.

1. Switch to sky-dome clouds

Cloud Fly Option = Not Possible to Fly Through is the biggest single saving. It switches from full volumetric clouds to a cheap sky-dome that looks similar from the ground. Only enable fly-through clouds if your game has flight or aerial cameras.

2. Drop cloud quality

Cloud Quality = Performance is the sweet spot for shipping games on mid-tier hardware. Drop to Ultra Performance for low-end. Ultra Quality is for cinematics where the camera lingers on cloud detail.

3. Tighten the cloud raymarcher

Lower Tracing Start Max Distance and Tracing Max Distance. The visible difference is mainly at the horizon, but the cost saving is meaningful.

4. Cap the sky update rate

Single Player FPS Lock to 30 FPS or 60 FPS caps how often the sky updates. Time still progresses smoothly to the eye; the sky just refreshes its samples less often.

5. Disable volumetric fog

Enable Volumetric Fog = false saves a lot. You lose god-rays and fog scattering effects, but your frame budget recovers.

If you keep volumetric fog on, lower Volumetric Fog Extinction Scale. It is the most expensive parameter on that pass.

6. Disable shadows you do not need

Each of these is a separate shadow source:

• Sun Cast Shadows
• Sky Light Cast Shadows
• Moon Cast Shadows

If your game does not need night-time directional shadows, turn off Moon Cast Shadows first. If your sky light is mostly ambient fill, Sky Light Cast Shadows can usually go.

7. Disable occlusion if your game has no interiors

Auto Add Occlusion = false saves the per-frame raycasts the indoor occlusion system performs. Only do this if the game truly has no covered spaces; otherwise interior lighting will look like daytime.

Multiplayer

Use System Mode = Multiplayer for any networked game. It changes how the sky replicates and avoids per-frame churn that happens when each client runs its own simulation in Single Player mode.

Tip

Profile before tuning. Unreal’s stat unit and stat gpu tell you whether the sky is actually your bottleneck. The biggest wins above are usually on GPU; if your bottleneck is CPU, the cloud raymarcher knobs do less and the FPS lock does more.

Where to next

• Clouds reference: every cloud setting
• Fog and atmosphere reference: every fog setting