Ue Uds Performance Mobile Troubleshooting

UDS performance, mobile, updates, and troubleshooting

This skill covers GPU/CPU performance levers, mobile configuration, the update workflow, modifying UDS safely, the runtime cache system, and the bulk of common runtime issues. For SKILL.md size reasons the deepest troubleshooting tables live here (intentionally consolidated rather than scattered across the other skills).

When to use this skill

• Frame rate is bad and you want to know what's costing the most.
• Building for mobile or a console with limited feature support.
• A UDS runtime variable change is delayed or has no effect.
• Updating the UDS plugin from the launcher.
• Something is rendering wrong (black, dark, hard lines, flickering, missing).
• Diagnosing single-layer water lighting wrong under clouds.

Performance — most impactful levers

Focused on UDS-specific features. General engine perf concerns (dynamic shadows, GI, etc.) apply the same way with or without UDS.

Sky Mode (largest GPU lever)

From most expensive to cheapest:

Color Mode

Project Mode

Volumetric Clouds perf

2D Dynamic Clouds perf

Sky Light perf

Volumetric Fog perf

CPU / tick perf

Material quality

Almost all UDS materials respond to global material quality. At Low/Medium material quality, complexity drops automatically.

Static / stationary lighting

Movable is the default, but static / stationary is always cheaper if it fits the project. See ue-uds-lighting-and-shadows for setup.

Mobile

Mobile Space Layer

Project setting Mobile DBuffer Decals must be enabled and supported by the platform for the Space Layer to render on mobile.

Runtime cache system (why property changes behave strangely)

UDS's runtime updates are split into three functions:

"Changing a property at runtime takes a second to apply"

Active properties (e.g. Sun Light Color) typically take 1–2 seconds because the cache is updating infrequently and interpolating between values.

"Changing a property at runtime has no effect"

These are static properties — applied at startup, not re-applied actively.

Updating UDS

Updates can install without losing your work. Always back up or use version control before updating so you can roll back.

If UDS is in its default location (Content/UltraDynamicSky/)

Copy code
1. Close your project
2. Launcher → Fab library → Library tab → find UDS
3. Add to Project → allow overwrite

If the launcher won't add or doesn't grab the latest version:
   Remove Local Content on UDS → try again

If UDS has been moved from its default location

More involved — you'll have to do the move in another project and copy it over.

Copy code
1. In your target project: right-click UltraDynamicSky folder
   → Update Redirector References (ensures no redirector reliance)
   Close target project.

2. From the launcher: add UDS to a blank project in the same engine version.

3. Open the blank project → open UDS demo map → let shaders compile.
   With the demo map open, move the UltraDynamicSky folder to the
   exact directory matching its location in the target project.
   Wait for the move; right-click the entire Content folder
   → Update Redirector References.

4. Close + open the UDS demo map in the blank project to verify
   nothing broke. If clouds aren't visible, run console command:
       Recompileshaders All
   (engine bug after asset moves)

5. Close both projects. From a file explorer, copy the
   UltraDynamicSky folder from the blank project over the one
   in the target project (overwriting).

6. Open the target project. Update is applied.

After the update, read the change log (linked from the docs home page) for any project work needed.

Modifying UDS (survives updates)

Work in a child class rather than editing UDS directly. See ue-uds-modifiers-configs-state for the full pattern.

Common Issues — lighting & post processing

Scene renders black after adding UDS

Almost certainly exposure. Try in order:

Copy code
1. Check level for post process volumes overriding exposure
   → disable the overrides so UDS can control exposure
2. Viewport Lit dropdown → check Game Settings for exposure
3. On UDS → Exposure category → disable Apply Exposure Settings

Ambient light doesn't update as time changes

Sky light isn't updating. Causes:

Ambient light slow to adapt after fast sky change

That's Lumen's default GI update speed. UDS doesn't touch Lumen. Adjust Lumen Global Illumination → Update Speed in a post-process volume. Raises GPU cost.

Water/ocean shader lit incorrectly in cloudy weather

Single-layer water tests directional light intensity/color without light functions.

Common Issues — volumetric clouds

Common Issues — general rendering

Multiplayer notes (perf-relevant)

Time of Day and Date replicate via Replicated Time of Day periodic syncs. Clients tick time locally between updates so the wire traffic is minimal. Weather state in UDW replicates similarly via state-source asset references rather than direct state values (see ue-udw-setup-and-state replication notes).

References & source material

Docs (Ultra Dynamic Sky 9.5):

• Configuring For Performance
• Considerations for Mobile
• How to Update UDS
• Modifying UDS Blueprints
• Common Issues — Lighting and Post Processing
• Common Issues — Volumetric Clouds
• Common Issues — General Rendering
• Changing a Property at Runtime Takes a Second to Apply
• Changing a Property at Runtime Has No Effect
• Technical Notes — Cache System
• Technical Notes — Replication (UDS)

Related skills: ue-uds-setup-and-modes (Sky / Color / Project / Feature Mode selection — the biggest perf decisions), ue-uds-clouds (full cloud settings; cloud rendering troubleshooting), ue-uds-lighting-and-shadows (Sky Light Mode tradeoffs; static lighting; exposure), ue-uds-fog-and-atmosphere (Volumetric Fog cost; hard fog lines; sky atmosphere position), ue-uds-modifiers-configs-state (child blueprints for modifying UDS), ue-udw-spatial-weather (child class pattern for Weather Override Volume).