Effect	Type	Driven by
Surface Weather Effects	Material function	Material wetness / snow / dust
Dynamic Landscape Weather Effects V3 (DLWE)	Material function	Material wetness / snow / dust + DLWE Interaction component
Glass Window Rain Drips	Material function	Rain
Foliage Wind Movement	Material function (WPO)	Wind
Water Surface Rain Ripples	Material function	Rain
Rainbow	Material in sky / screen	Rain + fog + sun exposure
Screen Droplets	Screen effect	Rain + camera facing
Screen Frost	Screen effect	Snow / material snow / manual
Heat Distortion	Post process	Temperature (or manual)
Post Process Wind Fog	Post process	Fog / Rain / Snow / Dust + wind
Puddle Fluid Volume	Actor (real water mesh)	Weather state
Dripping Mesh Particles	Niagara on mesh	Rain / material wetness
Freezing Breath	Niagara on actor	Cold temperature
Rain Drip Spline	Spline actor	Rain (+ optional icicles in cold)
Weather Occlusion Volume	Volume texture	Distance field

When to use this skill

Making props or scenery materials respond to weather (wet, snowy, dusty).
Adding footprints/tire tracks in snow or sand (landscape).
Adding puddles to a landscape; a real water puddle in a recess.
Rain drops dripping on glass windows.
Foliage swaying in the wind.
Rain ripples on water surfaces.
Rainbow after a storm.
Camera effects (droplets on the lens, frost, heat haze).
Character breath visible in cold weather.
Water dripping from a roof edge, or icicles hanging.

Material Effects Overview

UDW exposes material functions that make your materials respond to weather's changing material state:

Function	Use for
Surface Weather Effects	Solid surfaces (props, architecture) — not landscapes
Dynamic Landscape Weather Effects V3 (DLWE)	Landscapes / ground meshes; supports interactive trails and ripples
Glass Window Rain Drips	Flat translucent glass
Foliage Wind Movement	Foliage models (WPO)
Water Surface Rain Ripples	Water surface normal

Simulate Changing Material State Over Time

In the Material Effects category on UDW.

Setting	Behavior at runtime
Enabled (default)	Runtime material state changes gradually as weather changes (snow gradually accumulates while it snows)
Disabled	Runtime material state matches weather state directly. Changing Snow → Partly Cloudy makes Material Snow Coverage drop to 0 instantly. Required for Sequencer keyframes to play back identically.

The time over which each transition happens (per weather type) is set in the same category.

Surface Weather Effects

For solid scenery: props, architecture, decorations.

Setup

1. Material palette → search "Weather" → Surface Weather Effects
2. Place at end of material graph, before material result
3. Uses Material Attributes pin (in + out)
   If your material doesn't use one, wrap with Make/Break Material Attributes
4. Static Bool nodes for "Apply Wetness" + "Apply Snow / Dust"
   Disabling unused effects reduces material complexity
5. Default UVs are world space (good for static scenery)
   For moving / skeletal: plug True into "Local Space" or "For Skeletal Mesh"

Dripping and Droplets

Optional effects on wet surfaces, enabled via True into the Dripping and Droplets inputs.

Effect	Look
Dripping	Rivulets of water moving down where wet
Droplets	Small water beads clinging to a smooth surface

Both influenced by Porosity (0–1):

Porosity	Surface example
0	Car paint, plastic (smooth)
1	Concrete, sand (rough)
(unwired)	Derived from material roughness

Snow/Dust direction on rotating models

With Local Space or For Skeletal Mesh on, snow/dust uses the local normal — so it rotates with the model (snow on the side of a tipped-over object).

Fix: add the Material Snow Dust Reorient component as a child of the mesh. On begin play, add the dynamic material instance(s) using weather effects to the component's Dynamic Material Instances array. The component monitors rotation and slowly reorients snow/dust to face global up.

Dynamic Landscape Weather Effects V3 (DLWE)

For landscapes and large ground meshes. More involved than Surface Weather Effects. Example in the UDS demo map.

Setup

1. Material palette → search "Weather" → Dynamic Landscape Weather Effects V3
2. End of material graph, before material result
3. Uses material attributes pin (in + out) — same wrap pattern if needed
4. Static bools for "Apply Snow/Dust" + "Apply Wetness/Puddles"

Interactions (Trails and Ripples)

Moving actors can leave trails in snow/dust and ripples in puddles via the DLWE Interaction component.

Add as a scene component, parented to any moving component on an actor, or to a bone. e.g. character footprints in snow → one DLWE Interaction component per foot, parented to each foot socket.

Setting	Effect
`Size`	How far interaction effects spread and how big the effects are. Match the diameter of the object it represents.
DLWE Interaction Settings asset	The full interaction configuration the component references. Use the default or create your own.

Render Target Area

Snow/dust trail interactions only happen within a render target area around the player. Scale: Snow/Dust Interaction Render Target Area on UDW.

The target dynamically recenters as the player pawn moves. To recenter from a different location, change Control Point Location Source in Basic Controls on UDW.

Nanite Tessellation

DLWE supports nanite tessellation for snow/dust depth on nanite landscapes.

1. Project Settings: enable Nanite Tessellation
2. Material: check "Enable Tessellation"
3. Landscape actor: enable Nanite + build nanite mesh
4. DLWE node: plug True into "For Nanite Tessellation"
5. Set "Nanite Tessellation Magnitude" + "Nanite Tessellation Center"
   to match the material's tessellation settings.
   New landscape material with no existing displacement: Magnitude=1, Center=0
6. If you have existing displacement: plug False into
   "Displacement Input is World Scale" to keep DLWE from modifying it

Blocking interaction effects with physical materials

Arrays on UDW, advanced dropdown of DLWE category:

Array	Effect
`Physical Materials Which Disable Snow/Dust Sounds And Particles`	Phys mats in this array block snow/dust interaction effects
`Physical Materials Which Disable Puddle Sounds And Particles`	Same for puddles

Using DLWE on non-landscape meshes

To make Interaction components respond to surfaces other than landscape actors:

Add physical materials for those surfaces to Physical Materials which Enable DLWE Interactions on Non-Landscapes in the DLWE Interaction Settings asset.
Ensure static meshes use those phys mats.

Virtual Shadow Maps

Set the landscape's Shadow Cache Invalidation Behavior to Rigid — keeps the WPO and Pixel Depth Offset used for snow depth from constantly invalidating shadows.

Applying trail effect to underlying landscape layers

For other landscape layers (mud, sand) to also receive the snow/dust trail effect:

1. In material: give DLWE a "Custom Trail Surface Mask" input
   (0-1, typically from landscape layer samples)
2. In DLWE Interaction Settings asset:
   Add the relevant phys materials to
   "Custom Trail Surface Physical Materials"
   → component draws trails against those phys mats
     even with no snow/dust coverage present

Custom surface depth ranges from 0 to snow depth, scaled by the Custom Trail Surface Mask. Nanite tessellation gives the most convincing result.

DLWE Interactions Not Happening

Landscape needs World Static simple collision responding to queries and blocking Visibility. (Non-landscapes: see above.)
DLWE Interaction component positioned and sized to trigger interactions.
Control Point Location Source in advanced dropdown of Basic Controls — DLWE interactions happen around this point. Far camera = no visible effects.

Glass Window Rain Drips

Refractive water droplets dripping down thin glass surfaces. Translucent materials only.

Setup

1. Material palette → search "Weather" → Glass Window Rain Drips
2. Modifies Base Color + Opacity
   Outputs Base Color, Emissive Color, Opacity
   Use all three outputs for material result
3. UVs default to world space
   For moving surfaces, replace via the UVs input

Foliage Wind Movement

Outputs world position offset for noise-based foliage movement based on UDW's wind. Foliage-focused.

If your foliage already has wind setup, it may be simpler to modify those effects to reference UDW's wind via the Sample UDW Wind node instead.

Movement layers

Layer	Frequency	Use for
Small Movement	High	Leaves, grass blades, branch tips
Medium Movement	Middle	Whole branches
Large Movement	Low	Entire mesh swaying with gusts

All three on by default. Individually disable via Apply inputs.

Masking

Each layer has a 0–1 mask input multiplied over its strength. Foliage models typically have vertex color channels for masking — inspect the model's vertex colors to know which channel does what.

Small Movement requires a mask input. Medium and Large auto-generate a simple mask if none is supplied (using position relative to the pivot); model-aware vertex masks are always better.

For foliage master materials, expose movement inputs as parameters for per-instance tuning.

Water Surface Rain Ripples

Adds ripples to water surface normal based on rain amount.

Setup

1. Material palette → search "Weather" → Water Surface Rain Ripples
2. End of material graph, before result
3. Only modifies normal —
   plug in your material's normal, plug output's normal into result
4. Two additional inputs: scale the ripple texture, adjust intensity on normal

Controlling Your Own Material Effects with UDW

For custom material logic to react to UDW:

Material node	Output
Sample UDW Material State	Material snow coverage, material dust coverage, material wetness. Also applies WOV + Weather Mask effects (like the weather effect functions do by default).
Sample UDW Season	0–1 per season (total = 1)
Sample UDW Wind	Direction + intensity values/vectors

Or reference the shared MPC Ultra Dynamic Weather Parameters at Materials/Weather/ directly.

Rainbow

Enable in Rainbow category on UDW.

Condition for visibility	Detail
Rain or fog contributing	Amount each contributes is set in Rainbow settings
Camera directly exposed to sunlight	Affected by cloud coverage; under overcast → no rainbow
Sun low enough for rainbow above horizon, OR camera high enough to see it from above	Geometric constraint

Settings: rainbow visibility above cloud layer and below water level (if water level on).

Screen Droplets

Water droplets on the screen when the camera is exposed to rain. Enable in Screen Droplets category.

Setting	Effect
Droplet texture size	Visual scale
Effect strength	Intensity
Camera-facing dependency	How much the effect depends on facing the rain
Underwater behavior (automatic with UDS Water Level)	Turns off underwater; reapplies wet effect on resurface

Screen Frost

Frost/ice forming on the camera in snowy weather. Settings in Screen Frost category.

Trigger	Detail
Snow value	Weather state
Material snow	Material state
Manual contribution	Manually drive frost independent of weather
Form Duration / Clear Duration	Time to form/clear
Interior masking (default)	No frost when player is occluded (driven by Player Occlusion on UDS)

Heat Distortion

Post process effect distorting distant scenery with a shimmering/convection noise — heat haze. Category: Heat Distortion.

Mode	Source
Default	Calculated temperature value (see `ue-udw-random-seasons-temperature`)
Manual Heat Distortion	Add distortion independent of temperature

Post Process Wind Fog

Extra fog noise in the local area around the camera, moving with wind and weather particles. Post process effect — much cheaper than the equivalent volumetric fog effects.

Intensity scales with fog / rain / snow / dust in current weather state.

Masking in interiors:

Mask source	Detail
Weather Occlusion Volume (default, best)	Volume texture caching weather exposure around the camera via global distance field
Player Occlusion	Alternative

Puddle Fluid Volume

Renders a puddle as an actual water surface that moves up/down as the puddle fills/empties with weather. Use when there's a real geometric recess for water to fill.

In Blueprints/Weather_Effects/.

Optional Puddle Fluid Interactions renders the puddle as a dense grid mesh simulating natural ripples from DLWE Interaction components contacting the surface. Cost scales significantly with size — keep small.

Placement notes:

Detail	Reason
Editor preview state comes from currently selected weather on UDW	Override via Level Editor Preview State
Place so the puddle is fully hidden under ground when dry	Mesh visible in editor when dry (helps placement); hidden at runtime when dry
Scale via `Puddle Area` or actor scaling; only Z-axis rotation supported	Geometry constraint
Translucent water surface by default	Enable High Quality Translucency Reflections in project settings for good Lumen reflections

Categories: Puddle State (when/how filled/emptied), Fluid Interactions (DLWE interaction behavior toggles).

Dripping Mesh Particles

Niagara systems that make a mesh spawn drip particles on its surface in response to rain / material wetness. In Particles/Standalone/.

Mesh type	System	Setup
Static mesh	Dripping Static Mesh	Add Niagara component as a child of the static mesh component
Skeletal mesh	Dripping Skeletal Mesh	Same with skeletal mesh component

User parameters scale lifetime, max spawn rate, and the spawn rate fraction used when raining/wet/independent.

Drip appearance (sprite size, color, alpha) comes from UDW's rain particle settings.

If the actor has an Actor Weather Status component, the actor's local status drives the drip amount instead of global weather state. See ue-udw-setup-and-state.

Freezing Breath

Niagara system for visible character breath in cold air. Asset: Freezing Breath at Particles/Standalone/.

1. Add a Niagara component using Freezing Breath to your actor
2. Position + parent it in front of the mouth
3. Rotate so X axis points in direction of exhale

State	Behavior
Default	Visible in freezing temperatures (UDW's calculated local temperature)
With Actor Weather Status component	Uses actor-local temperature instead

Rain Drip Spline

Actor in Blueprints/Weather_Effects/ for spawning rain droplets along a line/curve — e.g. dripping from a building roof edge.

Drag in → small straight line. Edit the spline (move/rotate points; right-click to add) for length/shape.

Particle collision/appearance use UDW's rain particle settings.

Optional icicle meshes hanging from the spline render in cold weather — for icicles on a roof edge.

Icicles

For icicles hanging from mesh edges, see Rain Drip Spline above — the optional icicle feature along its spline.

Weather Occlusion Volume

Volume texture caching how occluded each point around the camera is from weather/wind. Built by sampling the global distance field — requires distance fields enabled and supported.

Used by Post Process Wind Fog to mask intensity in spaces blocked by scenery.

Water Level effects (UDW side)

The Use UDS Water Level option in UDW's Water Level category enables UDS water level for several UDW features. Actual water level config is on UDS — see ue-uds-modifiers-configs-state.

What UDS water level affects on UDW:

Weather particles kept out of below-water space
Sound Occlusion fully occludes when camera goes below water
Screen Droplets auto-off underwater; screen wet effect on resurface
Rainbow masked beneath water level (when its option is on)
Surface Weather Effects + DLWE functions have inputs to mask coverage below water

Current Weather Display widget

UDW_Current_Weather_Display widget (widget designer → Ultra Dynamic Sky Widgets). Represents current weather as an icon by default, sourced via Get Display Name for Current Weather. Exposed settings switch to text display or read the current weather preset asset.

Gotchas

Material doesn't respond to weather — function isn't placed at the end of the material graph (before material result), or wrong Material Attributes wrap pattern.
Snow on a moving object goes the wrong direction — Local Space / For Skeletal Mesh is on (correctly), but the Material Snow Dust Reorient component isn't added. Add it as a child of the mesh and register the dynamic material instance.
DLWE trails don't appear — landscape needs World Static simple collision blocking Visibility (queries enabled). Or DLWE Interaction component is too small. Or Control Point Location Source is far from camera.
DLWE on a non-landscape mesh ignored — phys material missing from the Physical Materials which Enable DLWE Interactions on Non-Landscapes array.
Snow depth invalidates virtual shadow maps every frame — set landscape's Shadow Cache Invalidation Behavior to Rigid.
Glass Window Rain Drips wrong on a moving glass surface — UVs default to world space. Replace via the UVs input.
Foliage Wind Movement: Small Movement does nothing — Small Movement requires a mask input. Plug one in.
Rainbow never appears — cloud coverage is too high (camera not exposed to sunlight); or sun too high; or neither rain nor fog is contributing.
Screen Frost appearing indoors — Player Occlusion isn't detecting the interior. See ue-uds-modifiers-configs-state.
Heat Distortion always at max — calculated temperature is hot, OR Manual Heat Distortion is also driving it. Disable manual contribution.
Puddle Fluid Volume mesh visible at runtime in dry state — that's a bug only in the editor; at runtime the dry mesh is hidden. If it's visible at runtime, the puddle isn't fully under ground — place it lower.
Puddle Fluid Interactions performance terrible — fluid interaction simulation cost scales with puddle area. Keep to small puddles.
Freezing Breath always visible — Actor Weather Status component overriding to its local temperature (warmer than ambient). Tune the actor temperature inputs.
Dripping Mesh Particles ignoring weather — has an Actor Weather Status component on the actor; drip uses actor-local status instead of global state. Intended behavior.
Custom material with Sample UDW Material State ignoring WOV / Weather Mask — Sample UDW Material State already applies those by default. If you're not using it, you're not getting WOV/mask effects.

References & source material

Docs (Ultra Dynamic Weather 9.5):

Material Effects Overview (incl. Simulate Changing Material State Over Time)
Surface Weather Effects (setup, dripping/droplets, rotating models)
Dynamic Landscape Weather Effects (DLWE V3)
Glass Window Rain Drips
Foliage Wind Movement
Water Surface Rain Ripples
Controlling Your Own Material Effects with UDW (Sample UDW Material State / Season / Wind)
Puddle Fluid Volume
Applying Water Level to Weather
Post Process Wind Fog
Rainbow
Screen Droplets
Screen Frost
Heat Distortion
Current Weather Display Widget
Dripping Mesh Particles
Freezing Breath Particles
Rain Drip Spline
Icicles
Weather Occlusion Volume

Plugin asset paths:

Particles/Standalone/ — Freezing Breath, Dripping Static Mesh, Dripping Skeletal Mesh niagara systems
Blueprints/Weather_Effects/ — Puddle Fluid Volume actor, Rain Drip Spline actor
Blueprints/Weather_Effects/System/ — Material State Manager class
Materials/Weather/ — Ultra Dynamic Weather Parameters MPC
Material Snow Dust Reorient component (for moving models)
Widget designer palette → Ultra Dynamic Sky Widgets → UDW_Current_Weather_Display

Related skills: ue-udw-setup-and-state (weather/material state drives everything; Actor Weather Status for per-actor effects), ue-udw-random-seasons-temperature (temperature drives Freezing Breath, Heat Distortion, icicles), ue-udw-spatial-weather (Weather Mask system masks material effects), ue-udw-particles-lightning-wind-sounds (Foliage Wind references UDW wind state), ue-uds-modifiers-configs-state (UDS Water Level config; Player Occlusion drives Screen Frost interior masking), ue-uds-fog-and-atmosphere (Global Volumetric Material is the volumetric counterpart of Post Process Wind Fog).

ue-udw-material-and-screen-effects

UDW material and screen effects