UKismetMathLibrary::GetReflectionVector

function Engine Blueprint Since 4.0

#include "Kismet/KismetMathLibrary.h"

Access: public Specifiers: staticBlueprintPure

Description

Reflects a direction vector across a surface normal, like a laser bouncing off a mirror. Equivalent to Direction - 2*(Direction dot SurfaceNormal)*SurfaceNormal.

Caveats & Gotchas

• SurfaceNormal should be a unit vector. Passing a non-normalized normal scales the reflected vector incorrectly — normalize it first with Normal() or use FHitResult.ImpactNormal which is already unit.
• This function and MirrorVectorByNormal perform the same mathematical operation. GetReflectionVector is the preferred name in modern UE usage and has the ScriptMethod alias 'MirrorByVector'; prefer it over MirrorVectorByNormal in new code.

Signature

static UE_INL_API FVector GetReflectionVector(FVector Direction, FVector SurfaceNormal);

Parameters

Name	Type	Description	Default
Direction	FVector	Incoming direction vector (does not need to be normalized).	—
SurfaceNormal	FVector	The normal of the surface to reflect across. Should be unit length.	—

Return Type

FVector

Example

Ricochet projectile off a surface C++

void AProjectile::OnHit(const FHitResult& Hit)
{
    FVector NewDir = UKismetMathLibrary::GetReflectionVector(
        GetVelocity().GetSafeNormal(), Hit.ImpactNormal);
    ProjectileMovement->Velocity = NewDir * GetVelocity().Size() * Bounciness;
}

Version History

Introduced in: 4.0

Version	Status	Notes
5.6	stable	—

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