UKismetMathLibrary::VectorSpringInterp

function Engine Blueprint Since 4.26

#include "Kismet/KismetMathLibrary.h"

Access: public Specifiers: staticBlueprintCallable

Description

Interpolates a vector using a damped spring model, producing natural overshoot and oscillation. Maintains velocity state between frames via FVectorSpringState.

Caveats & Gotchas

• SpringState must be stored as a persistent member variable — one per spring instance. Sharing state across multiple calls or reinitializing it every frame will corrupt the velocity accumulation and produce jitter or no movement.
• Set TargetVelocityAmount to 0 when using this to smooth sensor or animation data. A value of 1 causes the spring to anticipate the target's motion, which looks great for tracking a moving target but amplifies noise in fast-changing input.

Signature

static ENGINE_API FVector VectorSpringInterp(FVector Current, FVector Target, UPARAM(ref) FVectorSpringState& SpringState, float Stiffness, float CriticalDampingFactor, float DeltaTime, float Mass = 1.f, float TargetVelocityAmount = 1.f, bool bClamp = false, FVector MinValue = FVector(-1.f), FVector MaxValue = FVector(1.f), bool bInitializeFromTarget = false);

Parameters

Name	Type	Description	Default
Current	FVector	The current value this frame.	—
Target	FVector	The target value to spring toward.	—
SpringState	UPARAM(ref) FVectorSpringState&	Persistent state struct (velocity, etc.) — must be a unique variable per spring instance.	—
Stiffness	float	Spring stiffness. Higher values oscillate faster.	—
CriticalDampingFactor	float	Damping ratio. 0 = no damping (oscillates forever), 1 = critically damped (no oscillation), >1 = overdamped (slow return).	—
DeltaTime	float	Time elapsed since last call.	—
Mass	float	Simulated mass. Higher mass means slower acceleration.	1.f
TargetVelocityAmount	float	0–1 blend of how much the target's velocity influences the spring. Set to 0 when smoothing noisy data.	1.f
bClamp	bool	When true, output is clamped to [MinValue, MaxValue] per-axis and velocity is cancelled at limits.	false
MinValue	FVector	Per-axis minimum output clamp (used when bClamp=true).	FVector(-1.f)
MaxValue	FVector	Per-axis maximum output clamp (used when bClamp=true).	FVector(1.f)
bInitializeFromTarget	bool	If true, initializes Current from Target on the first update to avoid a large initial impulse.	false

Return Type

FVector

Example

Spring-follow a target location C++

// Header:
FVectorSpringState SpringState;

// Tick:
FVector NewPos = UKismetMathLibrary::VectorSpringInterp(
    GetActorLocation(), TargetActor->GetActorLocation(),
    SpringState, 100.f, 0.7f, DeltaTime);
SetActorLocation(NewPos);

Version History

Introduced in: 4.26

Version	Status	Notes
5.6	stable	—

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