Smear

Purpose

UOverAnimSmearModule is an Offset / Smear module that uses Pose History and surface velocity to stretch the mesh surface with a time delay along the direction of motion.

Header: OverAnimation/Asset/OverAnimModule.h
Class: UOverAnimSmearModule
Execution Phase: Offset / Smear (EOverAnimModulePhase::Smear)
Default Input Composition: Re-Skinning

Shared by Simple and Details

Module Id, Module Name, enabled state, and Order Within Module Phase are managed by the Module Stack and are therefore omitted from this Details reference. Input Composition is a shared module property exposed in Details.

UI name	Owning C++ property	Default / range	Effect
Master Effect Intensity	`UOverAnimMeshDeformer::MasterEffectIntensity`	`1.0` / minimum `0.0`, UI maximum `3.0`	Asset-wide value also shown in the selected module's Details. It scales authored strength for all modules in the asset, while each module's safety limits remain independent.

UI name	C++ property	Default / range	Effect
Input Composition	`CompositionMode`	`Re-Skinning`	Re-skins from the current control-point transform. The Smear constructor sets this value to `Re-Skinning`.
Length	`SimpleLength`	`1.0` / `0–5`	Ratio applied to authored `Buffer Size`. `2.0` doubles the pose-history frame count. It is shown only in `Simple`, but is always applied at runtime.
Density	`SimpleDensity`	`1.0` / `0–5`	Ratio applied to authored `Noise Density`. It changes only the break-up frequency, not depth or displacement amount. It has no effect when `Use Noise` is off.

Runtime interpretation of Simple knobs

Simple knobs do not modify Detailed values. Runtime resolves the following values from authored Detailed values regardless of the current layout.

Simple knob	Resolved property	Processing
`SimpleLength`	`NumFrames`	Applies a ratio to the authored frame count, rounds it, then limits it to `2–64`. There is no separate property for pose spacing.
`SimpleDensity`	`NoiseDensity`	Applies a ratio to authored density and limits it to a minimum of `0`. It is used in the result only when `bUseNoise == true`.

Details: Buffer

UI name	C++ property	Default / range	Effect and relationship
Buffer Size	`NumFrames`	`2` / `2–64`	Authored pose-sample count. Runtime limits the final frame count after multiplying by `SimpleLength` to `2–64`. Larger values retain longer pose history and consume memory proportional to control-point count.
Transform Buffer Space	`TransformBufferSpace`	`Component Space` (`Local`)	`Component Space` replays delayed animation poses relative to their parents. `World Space` realigns past world motion to the current component frame to preserve inertial trailing.
History Source	`HistorySource`	`Source Animation Pose`	`Source Animation Pose` reads history and velocity from the original animation pose and velocity. `Simulated Guide` reads the preceding procedural guide result. This choice determines both position and angular-velocity sources even when Angular Velocity is enabled.

`EOverAnimTransformBufferSpace`

The BlueprintType enum used by TransformBufferSpace.

C++ value	Editor UI	Meaning
`Local`	`Component Space`	Stores parent-relative animation poses in history and replays them with delay.
`World`	`World Space`	Rebases past world motion to the current Skeletal Mesh Component frame to preserve trailing inertia.

`EOverAnimTransformHistorySource`

The BlueprintType enum used by HistorySource.

C++ value	Editor UI	Meaning
`SourceAnimationPose`	`Source Animation Pose`	Uses the original animation pose and velocity derived from it as history input.
`SimulatedGuide`	`Simulated Guide`	Uses the preceding procedural guide result and its velocity as history input.

Details: Activation, Smear, Threshold, Noise

UI name	C++ property	Default / range	Visibility	Effect
Driver Mode	`DriverMode`	`Automatic + Signal Boost`	Always	`Automatic Motion` keeps only pose-driven behavior and rejects Signals. `Signal Gated Motion` applies Smear only while a response envelope is active. `Automatic + Signal Boost` retains pose-driven behavior and weights history usage during a response.
Include Angular Velocity	`bUseAngularVelocity`	`true`	Always	Adds tangential surface velocity caused by bone angular velocity. When enabled, the runtime proxy also creates angular-velocity and control-point-position arrays.
Use Velocity Threshold	`bUseVelocityThreshold`	`false`	Always	Suppresses Smear until the final surface velocity exceeds the threshold.
Velocity Threshold	`VelocityThreshold`	`0.0 cm/s` / minimum `0.0`	When `Use Velocity Threshold` is enabled	Minimum final surface velocity after combining linear and rotational components. It is not an angular-velocity-only threshold.
Use Noise	`bUseNoise`	`true`	Always	Determines whether to use Perlin-field-based break-up.
Noise Density	`NoiseDensity`	`50.0` / minimum `0.0`	When `Use Noise` is enabled	Authored frequency of the UV-space Perlin field. `SimpleDensity` is always applied to the final value. Higher values produce denser break-up.

`EOverAnimSmearDriverMode`

Value	UI name	Signal/Response effect
`MotionOnly`	Automatic Motion	Retains pose-history-driven behavior only. `SupportsSignals()` is false and Response Rule requests are rejected.
`SignalGatedMotion`	Signal Gated Motion	Applies Smear only when an active response envelope exists. Supports `Pulse` and `Sustained` Responses.
`MotionWithSignalBoost`	Automatic + Signal Boost	Retains procedural Smear while active responses weight history usage. Supports `Pulse` and `Sustained` Responses.

Execution · Signal · Response scope

Item	Support
Signal	Supported only when `Driver Mode` is not `Automatic Motion`.
Response Mode	`Pulse`, `Sustained`
Response Parameters	`FOverAnimSmearResponseParameters`
Automatic Six-Stage Motion	Conditionally supported. The module must be enabled and named, use a Signal-receiving `Driver Mode`, and have `Buffer Size >= 2`. Default automatic stage settings disable `Anticipation`, `Recoil`, and `Settle`, and set `Overshoot Strength` to `0.45`.
Pulse / Sustained timing	Both are allowed when `Driver Mode` permits Signals.

Automatic Motion does not receive Signal requests. In this mode, a Response Rule is rejected even if it reaches the module instance.

Response Rule parameters and Signal conditions

The Module Parameters of a Response Rule use FOverAnimSmearResponseParameters.

UI name	C++ property	Default / range	Effect
History Strength at Full Response	`HistoryStrengthAtMax`	`1.0` / `0.0–1.0`	Fraction of configured pose history used at maximum response. Trail direction and the affected silhouette continue to be determined by motion.

Runtime checks that this parameter is finite and within 0.0–1.0. Request weight is ResolvedMagnitude × Master Effect Intensity × HistoryStrengthAtMax, limited to 0.0–1.0.

Limitations and performance

When Driver Mode == Automatic Motion, SupportsSignals() is false, so Signal/Response requests are rejected.
Automatic Six-Stage Responses require the module to be enabled, a Module Name, a Signal-receiving Driver Mode, and Buffer Size >= 2.
Pose-history memory grows with the final frame count from authored Buffer Size × SimpleLength and the control-point count. Final frame count is limited to 2–64.
Angular-velocity and position data are passed to the runtime proxy only when Use Angular Velocity is enabled. The noise field is not used when Use Noise is disabled.