UKismetMathLibrary::Quat_IsIdentity

function Engine Blueprint Since 4.0

#include "Kismet/KismetMathLibrary.h"

Access: public Specifiers: staticBlueprintPure

Description

Returns true if the quaternion is approximately equal to the identity rotation (0, 0, 0, 1) within the given tolerance.

Caveats & Gotchas

• The header comment says this assumes the quaternion is already normalized — an un-normalized quaternion may return false even if it represents zero rotation once normalised.
• Like EqualEqual_QuatQuat, this checks components not rotation equivalence — the quaternion (0,0,0,-1) represents the same identity rotation but will fail this test.

Signature

static UE_INL_API bool Quat_IsIdentity(const FQuat& Q, float Tolerance = 1.e-4f)

Parameters

Name	Type	Description	Default
Q	const FQuat&	The quaternion to test.	—
Tolerance	float	Per-component tolerance for comparison with (0,0,0,1).	1.e-4f

Return Type

bool

Example

Skip rotation update when already at rest C++

FQuat DeltaRot = NewQuat * CurrentQuat.Inverse();
if (!UKismetMathLibrary::Quat_IsIdentity(DeltaRot))
{
    SetActorRotation((DeltaRot * GetActorQuat()).Rotator());
}

Version History

Introduced in: 4.0

Version	Status	Notes
5.6	stable	—

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