Ultra Dynamic Sky from Claude

Verified Oct 2026, UE 5.8.4, UDS content in /Game/UltraDynamicSky (Blueprints: Ultra_Dynamic_Sky, Ultra_Dynamic_Weather, Configuration_Manager, Volumetric_Cloud_Painter).

Adding it to a level

UDS brings its own sun, moon, sky light, sky atmosphere, height fog, volumetric clouds and a post-process component. Remove the level's DirectionalLight, SkyLight, SkyAtmosphere, ExponentialHeightFog, VolumetricCloud and any sky-sphere mesh first, then:

cls = unreal.EditorAssetLibrary.load_blueprint_class("/Game/UltraDynamicSky/Blueprints/Ultra_Dynamic_Sky")
uds = unreal.get_editor_subsystem(unreal.EditorActorSubsystem).spawn_actor_from_class(cls, unreal.Vector(0, 0, 0))

Defaults seen on spawn: Time of Day 960, Sky Mode "Volumetric Clouds", Cloud Coverage 3.8, Fog 1, Sun Light Intensity 5 (UDS's own scale, not physical lux), exposure = Histogram auto exposure. The actor draws an editor-only sun/moon target gizmo that shows up in MCP viewport captures even with bShowUI false (not in renders).

Reading and setting its variables

Python get_editor_property("time_of_day") does NOT find Blueprint variables with spaces. Use the Unreal MCP ObjectTools with the display name, lower-case first letter:

• ObjectTools.list_properties → JSON schema of every variable (~1000 keys, 330 KB; parse from the saved tool-result file). Keys look like "time of Day", "cloud Coverage", "exposure Bias Day".
• ObjectTools.get_properties(instance, ["time of Day", "fog"])
• ObjectTools.set_properties(instance, values='{"time of Day": 1030}') does NOT mark the actor's package dirty: save_dirty_packages skips it and a separate render process (MRQ new-process executor) reads the old values from disk. Call actor.modify() in Python before saving.
• UDS variables animate in Sequencer by variable name (float track, property name and path "Fog", "Time of Day"). fog is 0-10 (1 = light); raising it also blends the height fog falloff from base Height Fog Falloff (0.065) toward foggy Height Fog Falloff (0.015 = fog reaching high); a higher foggy falloff (e.g. 0.5) keeps the extra fog low.
• ObjectTools.set_properties — values is a JSON string. Enums are passed by name ("AEM_Histogram"); FloatRange as {"lowerBound": {"type": "Inclusive", "value": -1}, "upperBound": {"type": "Inclusive", "value": -1}}. The change applies in the editor right away (construction script reruns).

Locked exposure for renders

Auto exposure changes the brightness of everything (e.g. as a graphic colour fills the frame), so lock it for final renders:

• exposure Metering Mode = AEM_Manual → black frame: UDS's lights are scaled for auto exposure, while manual mode applies the physical camera EV (~10). Bias -10 still gave black in the editor capture (why not further explored).
• Works: keep AEM_Histogram and set exposure Brightness Range lower = upper (e.g. -1.0 → fixed EV100 -1, a good daylight value at Time of Day 960 with default sun). exposure Bias Day 0. EV100 1.5 was far too dark.
• Other exposure keys: exposure Bias Dawn/Dusk, exposure Bias Night, exposure Bias Cloudy, exposure Bias Foggy, exposure Compensation Curve, apply Exposure Settings.

Other keys worth knowing

animate Time of Day, sun Light Intensity, sky Light Intensity, sky Light Mode, render Exponential Height Fog, base Fog Density, scale Fog Density, use Volumetric Fog, dust Amount, enable Sun Lens Flare, enable Sun Light Shaft Bloom, simulate Real Sun, cinematic Clouds ... (sample counts used when the project mode is Cinematic/Offline).