FMath::Lerp
#include "Math/UnrealMathUtility.h"
Access: public
Specifiers: staticconstexpr
Description
Linearly interpolates between two values. Alpha is not clamped — values outside [0, 1] extrapolate beyond A and B.
Signature
template< class T, class U >
static constexpr UE_FORCEINLINE_HINT T Lerp(const T& A, const T& B, const U& Alpha)Parameters
| Name | Type | Description | Default |
|---|---|---|---|
| A | T | The start value (returned when Alpha is 0). | — |
| B | T | The end value (returned when Alpha is 1). | — |
| Alpha | U | The interpolation factor, typically in [0, 1]. | — |
Return Type
T Caveats & Gotchas
- • Alpha is unclamped. Pass FMath::Clamp(Alpha, 0.f, 1.f) explicitly if you need to guarantee the result stays between A and B.
- • For smooth frame-rate-independent interpolation, use FMath::FInterpTo instead — Lerp with a time-based alpha will drift as frame rate changes.
- • FQuat has a specialised TCustomLerp implementation that performs NLerp rather than component-wise lerp. For correct quaternion blending use FQuat::Slerp.
Example
Blend two colours and two floats C++
// Blend two colours based on damage fraction
float DamageFraction = FMath::Clamp(1.0f - (Health / MaxHealth), 0.0f, 1.0f);
FLinearColor DisplayColor = FMath::Lerp(FLinearColor::Green, FLinearColor::Red, DamageFraction);
// Lerp a FOV between two camera presets
float CurrentFOV = FMath::Lerp(DefaultFOV, AimFOV, AimAlpha);Tags
Version History
Introduced in: unknown
| Version | Status | Notes |
|---|---|---|
| 5.6 | stable | — |
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