UWorld::LineTraceMultiByChannel

function Engine Since 4.0

#include "Engine/World.h"

Access: public Specifiers: const

Description

Traces a ray from Start to End and returns all overlapping hits plus the first blocking hit. Results are sorted by distance; the blocking hit (if any) is always the last element. Returns true if OutHits contains any blocking hit.

Signature

bool LineTraceMultiByChannel( TArray<struct FHitResult>& OutHits, const FVector& Start, const FVector& End, ECollisionChannel TraceChannel, const FCollisionQueryParams& Params = FCollisionQueryParams::DefaultQueryParam, const FCollisionResponseParams& ResponseParam = FCollisionResponseParams::DefaultResponseParam ) const

Parameters

Name	Type	Description	Default
OutHits	TArray<struct FHitResult>&	Receives all hit results sorted by distance. The blocking hit (if any) is always the last element.	—
Start	const FVector&	World-space start point of the ray.	—
End	const FVector&	World-space end point of the ray.	—
TraceChannel	ECollisionChannel	Collision channel used to determine which components are hit.	—
Params	const FCollisionQueryParams&	Additional query options including ignored actors.	FCollisionQueryParams::DefaultQueryParam
ResponseParam	const FCollisionResponseParams&	Override collision response settings.	FCollisionResponseParams::DefaultResponseParam

Return Type

bool

Caveats & Gotchas

• The trace stops generating results after the first blocking hit — geometry behind the blocker is not tested.
• OutHits contains both overlapping and blocking hits. Check FHitResult::bBlockingHit on each result to distinguish them.
• OutHits is not cleared before use — clear it yourself if the array is reused across calls.

Example

Trace through multiple overlapping actors C++

TArray<FHitResult> Hits;
FCollisionQueryParams Params;
Params.AddIgnoredActor(this);

GetWorld()->LineTraceMultiByChannel(Hits, Start, End, ECC_Visibility, Params);

for (const FHitResult& Hit : Hits)
{
	if (Hit.bBlockingHit)
	{
		// First (and only) blocker
	}
}

Version History

Introduced in: 4.0

Version	Status	Notes
5.6	stable	—

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