FMath::SphereDistToLine

function Core Since 4.0

#include "Math/UnrealMathUtility.h"

Access: public Specifiers: static

Description

Finds the closest point on a sphere's surface to an infinite line. When the line intersects the sphere, the closest point on the sphere to LineOrigin is returned instead.

Caveats & Gotchas

• LineDir must be normalized. Passing a non-normalized direction produces incorrect results without any error — normalize it with GetSafeNormal() before calling.
• The returned point is on the sphere's surface, not the closest point along the line. If you want the closest point on the line to the sphere's centre, project SphereOrigin onto the line separately.
• The function does not return whether the line actually intersects the sphere — compute FVector::Dist(SphereOrigin, ClosestPointOnLine) < SphereRadius yourself if you need that flag.

Signature

static CORE_API void SphereDistToLine(FVector SphereOrigin, float SphereRadius, FVector LineOrigin, FVector LineDir, FVector& OutClosestPoint)

Parameters

Name	Type	Description	Default
SphereOrigin	FVector	Centre of the sphere.	—
SphereRadius	float	Radius of the sphere.	—
LineOrigin	FVector	A point on the infinite line.	—
LineDir	FVector	Direction of the line. Must be normalized.	—
OutClosestPoint	FVector&	Closest point on the sphere's surface to the line (or the projected point when the line intersects).	—

Return Type

void

Example

Compute where a laser beam grazes a sphere obstacle C++

FVector GrazePoint;
FMath::SphereDistToLine(
    ObstacleSphere.Center, ObstacleSphere.Radius,
    LaserOrigin, LaserDirection.GetSafeNormal(),
    GrazePoint
);
DrawDebugSphere(GetWorld(), GrazePoint, 5.f, 8, FColor::Orange);

Version History

Introduced in: 4.0

Version	Status	Notes
5.6	stable	—

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