Ue Udw Spatial Weather

UDW spatial weather

The systems that make weather happen somewhere specific rather than globally. WOVs and Radial Storms drive state per location; the Weather Mask system excludes material effects from interiors and under-roof areas.

When to use this skill

• Different weather in different parts of one level.
• A storm the player can see coming in from across the map.
• A storm that moves linearly across the level over time.
• Adjusting weather behavior when the camera goes above the cloud layer.
• Keeping snow accumulating inside a building, or wetness off the floor under a roof.

Weather Override Volumes (WOV)

Actor for region-specific weather. Found at Blueprints/Weather_Effects/.

The region shape is defined by the actor's spline component — edit spline points for any shape. Right-click on the spline to add new points. You can scale the actor; avoid non-uniform scaling.

WOV weather configuration mirrors UDW's global controls:

• Select a preset for the WOV in its Basic Controls category.
• Enable Random Weather Variation on the WOV with its own probability maps. Timing/logic specifics come from UDW's Random Weather Variation category.

Key WOV settings

Where the player is queried from

The location used to test against WOVs is set by Control Point Location Source in Basic Controls on UDW. Defaults to player pawn location.

Material state across the WOV boundary

By default, WOVs draw their material state into a render target sampled by the weather material functions, so:

• A snowy region appears snowy from outside.
• From inside, you see the lack of snow coverage outside.

Disable or adjust on UDW from the Weather Override Volumes category.

Runtime WOV functions

Custom Volume Behavior

To use a WOV for something other than weather (e.g. fire custom events when the player crosses into the region):

1. Create a child of the Weather Override Volume class
2. Override Custom Volume Behavior on the child

The function runs from UDW when the WOV affects local weather.
Input: Alpha (0-1) — how much the player is inside the volume.

Radial Storms

Circular weather region actor. Unique vs WOVs: can render its own local effects and local cloud coverage — players see the storm in the distance as a cloud formation with fog and obscured lightning beneath. Built to be dynamic — spawn at runtime, fade in/out, move linearly.

Constraints

Periodic spawning

UDW's Radial Storm Spawning category enables periodic randomized spawning during play. UDW spawns radial storms one at a time, placing/moving them so they pass over the player. The weather preset can be season-determined (similar to Random Weather Variation in ue-udw-random-seasons-temperature).

Manual spawning and control

You can spawn at runtime or place one in the editor — UDW's spawning system isn't required.

Example flow:

storm = SpawnActor(RadialStorm_BP, location)
storm.FadeInStorm(30)                              // 30s fade in
storm.MoveStormOverTime(targetPos, 200, true)      // 200s movement
// fade-out auto starts in last 30s of the movement

Weather Above Volumetric Clouds

When UDS's Sky Mode is Volumetric Clouds, UDW by default adjusts weather state when the player goes above the cloud layer.

Configurable in the Weather Above Volumetric Clouds category on UDW. Enable/disable the adjustments entirely, or change the multipliers per weather value used when above clouds.

Weather Mask System

Masks the material weather effects (snow, dust, wetness) in specific spaces — by default they affect everywhere globally.

Two component classes at Blueprints/Weather_Effects/Components/ draw into a weather mask render target sampled by the weather material functions. Use the components directly in your actors, or use wrapper actor classes in Blueprints/Weather_Effects/.

Weather Mask Brush

Draws a simple shape or a painted texture. The actor's Brush variable selects between them. Can be scaled non-uniformly and rotated on Z axis.

Because the system works by drawing into a render target, shapes are always projected straight down on Z axis.

Painted brush textures

For more control than simple shapes, paint a texture using the Weather Mask Brush Painter:

• Ultra Dynamic Sky dropdown on the level editor toolbar, or
• Blueprints/Tools/

With the painter open, select a weather mask brush actor and click the button to start painting. Controls:

When finished, click Save — painted mask saves to a texture in UDS_LevelData/ next to the level.

Weather Mask Projection Box

Captures meshes within the box and uses their shapes to mask weather effects straight down. Place around a complex structure (e.g. a building) and the mesh shapes occlude directly beneath them.

Placement tips:

• Place the box so it encompasses only the relevant mesh geometry. e.g. enclose just the roof of a house.
• Width/length as small as possible to fit the occluding geometry — eliminates wasted render-target resolution.

Material-level opt-out

Static switch parameters on individual materials/instances:

Mask distance and update

Mask effects stop at a certain distance from the camera, set by the render target width. Adjust in Weather Mask Target category on UDW.

Fading a mask component

WeatherMaskBrush.FadeMaskOverTime(duration)
// or
WeatherMaskProjectionBox.FadeMaskOverTime(duration)
// Default fade rate: 20 updates/sec.
// Adjust via Weather Mask Update Period on UDW.

Gotchas

• WOV transition looks abrupt — Transition Width is too small (default is). Make it much larger so the player crosses a smooth gradient.
• Radial Storm not visible from outside — Sky Mode isn't Volumetric Clouds. Distant-storm visuals require Volumetric Clouds; with other modes the storm still affects state but renders no visible distant storm.
• WOV not affecting weather — Control Point Location Source is set to a custom vector that isn't where the player is. Default to Player Pawn.
• Weather Mask not stopping snow inside a building — Weather Mask Brush or Projection Box not placed; or Mask Snow/Dust value too low; or render target distance exceeded.
• Mask Projection Box has artifacts — box is too large, wasting render-target resolution. Shrink to just enclose the occluding geometry.
• Material ignoring Weather Mask — Apply Weather Mask Brushes to Wetness/Snow static switches on the material are off.
• Snow visible outside the WOV from inside — Weather Override Volumes category on UDW has the material-state-rendering option turned off. Enable it for "snowy outside / not snowy inside" reads.
• Per-storm logic from a child class not running — for a WOV, override Custom Volume Behavior (not the parent's behavior). For a Radial Storm, similar pattern via child class.
• Wind direction not changing inside a WOV — Apply Wind Direction on the WOV is off. Enable for region-specific wind.

References & source material

Docs (Ultra Dynamic Weather 9.5):

• Weather Override Volumes
• Radial Storms
• Weather Above Volumetric Clouds
• Masking Material Effect Coverage (Weather Mask Brush, Weather Mask Projection Box)

Plugin asset paths:

• Blueprints/Weather_Effects/ — Weather Override Volume, Radial Storm, Weather Mask Brush, Weather Mask Projection Box actor classes
• Blueprints/Weather_Effects/Components/ — Weather Mask Brush and Projection Box component classes (for embedding in your own actors)
• Blueprints/Tools/ — Weather Mask Brush Painter editor utility
• UDS_LevelData/ (created next to the level) — painted weather mask textures

Related skills: ue-udw-setup-and-state, ue-udw-random-seasons-temperature, ue-udw-material-and-screen-effects, ue-uds-setup-and-modes (Volumetric Clouds required for Radial Storm distant visibility), ue-uds-modifiers-configs-state (UDS Occlusion Volume for forced player occlusion).