UKismetMathLibrary::Vector4_MirrorByVector3

function Engine Blueprint Since 4.0

#include "Kismet/KismetMathLibrary.h"

Access: public Specifiers: staticBlueprintPure

Description

Reflects a direction vector across a surface normal using only the XYZ components, equivalent to D - 2*(D·N)*N. Models specular reflection or a ray bouncing off a mirror surface.

Caveats & Gotchas

• SurfaceNormal should be normalized; passing a non-unit normal scales the reflected vector and produces an incorrect result without any warning.
• W is ignored for the computation but the returned vector's W component is taken from the input Direction's W — if your pipeline expects W=0 for directions, pass Direction with W=0.

Signature

static UE_INL_API FVector4 Vector4_MirrorByVector3(const FVector4& Direction, const FVector4& SurfaceNormal);

Parameters

Name	Type	Description	Default
Direction	const FVector4&	The incoming direction vector to reflect.	—
SurfaceNormal	const FVector4&	The surface normal to reflect across. Should be unit length for correct results.	—

Return Type

FVector4

Example

Reflect a projectile direction off a surface C++

FVector4 Velocity(1.0, 0.0, -1.0, 0.0);
FVector4 Normal(0.0, 0.0, 1.0, 0.0); // floor
FVector4 Reflected = UKismetMathLibrary::Vector4_MirrorByVector3(Velocity, Normal);
// Reflected == (1, 0, 1, 0)

Version History

Introduced in: 4.0

Version	Status	Notes
5.6	stable	—

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