UKismetMathLibrary::Quat_Exp

function Engine Blueprint Since 4.0

#include "Kismet/KismetMathLibrary.h"

Access: public Specifiers: staticUFUNCTIONBlueprintPure

Description

Computes the quaternion exponential, mapping a pure quaternion (W=0, V=theta*v) back to a unit quaternion via Exp(q) = (sin(theta)*v, cos(theta)). Used together with Quat_Log for quaternion calculus operations such as squad interpolation.

Caveats & Gotchas

• The input is expected to have W=0. Passing a general unit quaternion produces mathematically defined but physically meaningless results — this is not a general-purpose exponentiation.
• Quat_Exp and Quat_Log are inverse operations only for pure quaternions. Applying Log then Exp to an arbitrary unit quaternion does not round-trip perfectly when the quaternion has a non-zero W component.

Signature

static UE_INL_API FQuat Quat_Exp(const FQuat& Q);

Parameters

Name	Type	Description	Default
Q	const FQuat&	A pure quaternion (W=0) of the form theta*v where \|v\|=1.	—

Return Type

FQuat

Example

Round-trip through Log/Exp C++

FQuat Original = FQuat(FVector(0, 0, 1), FMath::DegreesToRadians(90.f));

// Log produces a pure quaternion
FQuat LogQ = UKismetMathLibrary::Quat_Log(Original);

// Exp recovers the original
FQuat Recovered = UKismetMathLibrary::Quat_Exp(LogQ);
// Recovered ≈ Original

Version History

Introduced in: 4.0

Version	Status	Notes
5.6	stable	—

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