FMath::SegmentTriangleIntersection

function Core Since 4.0

#include "Math/UnrealMathUtility.h"

Access: public Specifiers: static

Description

Tests whether a line segment intersects a triangle and returns both the intersection point and the triangle's face normal. Returns false if the segment misses or is parallel to the triangle.

Caveats & Gotchas

• The test is one-sided — the segment must approach from the front face (defined by counter-clockwise winding of A, B, C). A segment hitting the back face returns false. Reverse the winding or reverse the segment if you need back-face intersection.
• OutIntersectPoint and OutTriangleNormal are only valid on a true return.
• This is an exact geometric test, not a physics-engine query. For general mesh intersection queries use UWorld::LineTraceSingleByChannel instead — it leverages acceleration structures.

Signature

static CORE_API bool SegmentTriangleIntersection(const FVector& StartPoint, const FVector& EndPoint, const FVector& A, const FVector& B, const FVector& C, FVector& OutIntersectPoint, FVector& OutTriangleNormal)

Parameters

Name	Type	Description	Default
StartPoint	const FVector&	Start of the segment.	—
EndPoint	const FVector&	End of the segment.	—
A	const FVector&	First vertex of the triangle.	—
B	const FVector&	Second vertex of the triangle.	—
C	const FVector&	Third vertex of the triangle.	—
OutIntersectPoint	FVector&	Receives the intersection point on the triangle if the function returns true.	—
OutTriangleNormal	FVector&	Receives the triangle's face normal if the function returns true.	—

Return Type

bool

Example

Test a custom ray against a manually-specified triangle C++

FVector HitPoint, HitNormal;
if (FMath::SegmentTriangleIntersection(
    RayStart, RayEnd,
    TriVerts[0], TriVerts[1], TriVerts[2],
    HitPoint, HitNormal))
{
    UE_LOG(LogTemp, Log, TEXT("Hit at %s, normal %s"),
        *HitPoint.ToString(), *HitNormal.ToString());
}

Version History

Introduced in: 4.0

Version	Status	Notes
5.6	stable	—

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