UKismetMathLibrary::Vector_CosineAngle2D

function Engine Blueprint Since 4.0

#include "Kismet/KismetMathLibrary.h"

Access: public Specifiers: staticUFUNCTIONBlueprintPure

Description

Returns the cosine of the angle between two vectors projected onto the XY plane, ignoring Z. A result of 1.0 means the vectors face the same horizontal direction; -1.0 means opposite directions.

Caveats & Gotchas

• Z components are ignored entirely. Two vectors pointing in opposite horizontal directions but at different heights will still give -1.0.
• Returns the cosine, not the angle itself. Pass through FMath::Acos() to get the actual angle in radians.
• If either vector's 2D (XY) length is near-zero (e.g. pointing straight up/down), the result is undefined. Normalise or check the 2D size before calling.

Signature

static UE_INL_API double Vector_CosineAngle2D(FVector A, FVector B);

Parameters

Name	Type	Description	Default
A	FVector	First direction vector.	—
B	FVector	Second direction vector.	—

Return Type

double

Example

Check if an enemy is facing roughly toward the player C++

FVector EnemyForward = Enemy->GetActorForwardVector();
FVector ToPlayer = (Player->GetActorLocation() - Enemy->GetActorLocation()).GetSafeNormal();
double CosAngle = UKismetMathLibrary::Vector_CosineAngle2D(EnemyForward, ToPlayer);
bool bFacingPlayer = (CosAngle > 0.7); // roughly within 45 degrees

Version History

Introduced in: 4.0

Version	Status	Notes
5.6	stable	—

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