UKismetAnimationLibrary::K2_CalculateVelocityFromPositionHistory
#include "KismetAnimationLibrary.h"
Access: public
Specifiers: staticUFUNCTIONBlueprintCallable
Description
Tracks a position over successive calls and returns a smoothed scalar velocity magnitude, optionally normalized into a 0-1 range. Requires a persistent FPositionHistory variable to accumulate samples across calls.
Caveats & Gotchas
- • History must be backed by a variable that persists between calls (a member variable in C++, or a Blueprint variable passed by ref) — passing a temporary or freshly-constructed FPositionHistory every call means velocity is always computed from a single sample and produces near-zero or garbage results.
- • This is BlueprintCallable, not BlueprintPure — it has side effects (mutating History) each time it's called, so calling it multiple times per frame accumulates multiple samples and will skew the smoothing.
- • When VelocityMin and VelocityMax are both 0.0, normalization is disabled and the function returns the raw velocity magnitude instead of a 0-1 value.
Signature
static float K2_CalculateVelocityFromPositionHistory(float DeltaSeconds, FVector Position, UPARAM(ref) FPositionHistory& History, int32 NumberOfSamples, float VelocityMin, float VelocityMax)Parameters
| Name | Type | Description | Default |
|---|---|---|---|
| DeltaSeconds | float | Time passed in seconds since the last call. | — |
| Position | FVector | The position to track over time. | — |
| History | FPositionHistory& | Persistent storage for the position history; must be a variable that stays alive between calls. | — |
| NumberOfSamples | int32 | Number of samples to retain for the history — higher values smooth the velocity result more. | 16 |
| VelocityMin | float | Minimum velocity for normalization; if both min and max are 0, normalization is disabled. | 0.f |
| VelocityMax | float | Maximum velocity for normalization; if both min and max are 0, normalization is disabled. | 128.f |
Return Type
float Example
Track smoothed velocity for a moving actor C++
// FPositionHistory PositionHistory; // member variable, persists across ticks
const float Velocity = UKismetAnimationLibrary::K2_CalculateVelocityFromPositionHistory(
DeltaSeconds, GetActorLocation(), PositionHistory, 16, 0.0f, 128.0f);Tags
Version History
Introduced in: 4.0
| Version | Status | Notes |
|---|---|---|
| 5.6 | stable | — |
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