UKismetMathLibrary::Quat_GetRotationAxis

function Engine Blueprint Since 4.0

#include "Kismet/KismetMathLibrary.h"

Access: public Specifiers: staticUFUNCTIONBlueprintPure

Description

Returns the unit vector axis around which this quaternion rotates. For the identity quaternion (no rotation), returns FVector(1,0,0) as a defined fallback.

Caveats & Gotchas

• The identity quaternion has no meaningful rotation axis, so the engine returns FVector(1,0,0) rather than a zero vector. Check Quat_GetAngle before using this axis if you need to distinguish 'no rotation' from 'rotating around X'.
• This axis together with Quat_GetAngle gives the axis-angle representation of the quaternion. For the full decomposition, use both functions — do not assume the axis encodes magnitude.

Signature

static UE_INL_API FVector Quat_GetRotationAxis(const FQuat& Q);

Parameters

Name	Type	Description	Default
Q	const FQuat&	The quaternion to extract the rotation axis from.	—

Return Type

FVector

Example

Extract axis-angle for procedural animation C++

FQuat TwistQuat = GetComponentQuat();
FVector Axis  = UKismetMathLibrary::Quat_GetRotationAxis(TwistQuat);
float   Angle = UKismetMathLibrary::Quat_GetAngle(TwistQuat);
UE_LOG(LogTemp, Display, TEXT("Rotating %.1f deg around (%s)"),
    FMath::RadiansToDegrees(Angle), *Axis.ToString());

Version History

Introduced in: 4.0

Version	Status	Notes
5.6	stable	—

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