FMath::CriticallyDampedSmoothing
#include "Math/UnrealMathUtility.h"
Access: public
Specifiers: staticconstexpr
Description
Smooths a value using a critically-damped spring, tracking both position and velocity. Reaches the target without overshoot and correctly handles a moving target by anticipating its velocity.
Caveats & Gotchas
- • The approximation is accurate only when InDeltaTime < 0.5 * InSmoothingTime. At larger delta times (e.g. from a frame spike) the result remains well-behaved but less accurate.
- • InOutValueRate must be stored between frames and passed back each call — it is not a scratch value. Zeroing it every frame will cause jerky motion.
- • If InTargetValueRate is discontinuous (e.g. target suddenly changes velocity), the output velocity will also be discontinuous that frame. Smooth the target velocity separately if that's unacceptable.
Signature
template< class T >
static constexpr void CriticallyDampedSmoothing(T& InOutValue, T& InOutValueRate, const T& InTargetValue, const T& InTargetValueRate, const float InDeltaTime, const float InSmoothingTime)Parameters
| Name | Type | Description | Default |
|---|---|---|---|
| InOutValue | T& | The value to be smoothed. Modified in place. | — |
| InOutValueRate | T& | The rate of change of the value. Modified in place — persist this between frames. | — |
| InTargetValue | const T& | The target to smooth towards. | — |
| InTargetValueRate | const T& | The target rate of change. Pass zero if target is stationary. | — |
| InDeltaTime | const float | Elapsed time since last update. | — |
| InSmoothingTime | const float | Timescale over which to smooth. Larger values result in more smoothed behaviour. Can be zero. | — |
Return Type
void Example
Smooth camera arm length with velocity tracking C++
// In header:
float CurrentArmLength = 300.f;
float ArmLengthRate = 0.f;
// In Tick:
FMath::CriticallyDampedSmoothing(CurrentArmLength, ArmLengthRate, TargetArmLength, 0.f, DeltaTime, 0.15f);
SpringArm->TargetArmLength = CurrentArmLength;Tags
Version History
Introduced in: 4.20
| Version | Status | Notes |
|---|---|---|
| 5.6 | stable | — |
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