UBlueprintSpringMathLibrary::CriticalSpringDampFloat

function Engine Blueprint Since 5.7

#include "Kismet/BlueprintSpringMathLibrary.h"

Access: public Specifiers: staticBlueprintCallable

Description

Interpolates InOutX towards TargetX using the motion of a critically damped spring, storing the resulting velocity back into InOutV. Called once per tick to smoothly chase a moving target without overshoot ringing.

Caveats & Gotchas

• Marked UE_EXPERIMENTAL(5.7, "SpringMath is experimental") — behaviour and defaults may change in later engine versions.
• InOutX and InOutV are both in/out parameters that must be stored persistently by the caller (e.g. as member variables); passing fresh zero-initialized locals every call resets the spring state instead of continuing it.
• A SmoothingTime of 0 snaps InOutX directly to TargetX rather than interpolating — this is a valid way to disable smoothing conditionally, not an edge case to guard against.

Signature

static void CriticalSpringDampFloat(UPARAM(ref) float& InOutX, UPARAM(ref) float& InOutV, const float& TargetX, float DeltaTime, float SmoothingTime = 0.2f);

Parameters

Name	Type	Description	Default
InOutX	float&	The value to be damped; updated in place each call.	—
InOutV	float&	The velocity of the damped value; must be persisted by the caller between calls.	—
TargetX	const float&	The goal value to damp towards.	—
DeltaTime	float	Timestep in seconds.	—
SmoothingTime	float	Smoothing time for the spring. Larger values give more damped behaviour; 0 snaps InOutX to TargetX.	0.2f

Return Type

void

Example

Smooth a UI meter value towards a target each tick C++

// Members persisted on the owning object
float DisplayedHealth = 100.f;
float DisplayedHealthVelocity = 0.f;

void AMyHUDActor::Tick(float DeltaTime)
{
    Super::Tick(DeltaTime);
    UBlueprintSpringMathLibrary::CriticalSpringDampFloat(DisplayedHealth, DisplayedHealthVelocity, TargetHealth, DeltaTime, 0.15f);
}

Version History

Introduced in: 5.7

Version	Status	Notes
5.7	experimental	SpringMath is experimental.

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