UGameplayStatics::Blueprint_PredictProjectilePath_ByTraceChannel

function Engine Blueprint Since 4.15

#include "Kismet/GameplayStatics.h"

Access: public Specifiers: staticBlueprintCallable

Description

Simulates a projectile arc under gravity and returns the path positions, tracing against a single collision channel for blocking hits. Prefer this over the ObjectType variant when you have a dedicated projectile trace channel.

Caveats & Gotchas

• The default TraceChannel in Blueprint is ECC_WorldDynamic; many static geometry meshes use ECC_WorldStatic and will not block the trace unless you switch channels.
• Each simulation step performs a sphere sweep — high SimFrequency on long arcs can generate dozens of sweep tests per call, which is expensive in busy scenes.
• ProjectileRadius of 0 degrades the sweep to a line trace, which may miss narrow obstacles that the actual projectile would collide with.

Signature

static ENGINE_API bool Blueprint_PredictProjectilePath_ByTraceChannel(const UObject* WorldContextObject, FHitResult& OutHit, TArray<FVector>& OutPathPositions, FVector& OutLastTraceDestination, FVector StartPos, FVector LaunchVelocity, bool bTracePath, float ProjectileRadius, TEnumAsByte<ECollisionChannel> TraceChannel, bool bTraceComplex, const TArray<AActor*>& ActorsToIgnore, EDrawDebugTrace::Type DrawDebugType, float DrawDebugTime, float SimFrequency = 15.f, float MaxSimTime = 2.f, float OverrideGravityZ = 0);

Parameters

Name	Type	Description	Default
WorldContextObject	const UObject*	Any UObject within the world to provide world context.	—
OutHit	FHitResult&	Output: hit result if the simulated projectile hits something.	—
OutPathPositions	TArray<FVector>&	Output: ordered positions of the simulated arc from StartPos to end.	—
OutLastTraceDestination	FVector&	Output: goal position of the final trace step.	—
StartPos	FVector	Starting position of the projectile.	—
LaunchVelocity	FVector	Initial velocity of the simulated projectile.	—
bTracePath	bool	If true, sweeps along the arc checking for blocking hits.	—
ProjectileRadius	float	Radius of the simulated spherical projectile.	—
TraceChannel	TEnumAsByte<ECollisionChannel>	Collision channel to trace against.	—
bTraceComplex	bool	Whether to use complex collision geometry.	—
ActorsToIgnore	const TArray<AActor*>&	Actors to exclude from collision checks.	—
DrawDebugType	EDrawDebugTrace::Type	Controls debug visualization.	—
DrawDebugTime	float	Duration in seconds for debug lines.	—
SimFrequency	float	Simulation steps per second.	15.f
MaxSimTime	float	Maximum simulation time in seconds.	2.f
OverrideGravityZ	float	Optional gravity override; 0 uses world gravity.	0

Return Type

bool

Example

Predict throw arc for UI indicator C++

FHitResult Hit;
TArray<FVector> Path;
FVector LastDest;
TArray<AActor*> Ignored = { GetOwner() };

UGameplayStatics::Blueprint_PredictProjectilePath_ByTraceChannel(
    this, Hit, Path, LastDest,
    MuzzleLocation, ThrowVelocity,
    true, 5.f, ECC_WorldStatic,
    false, Ignored,
    EDrawDebugTrace::ForOneFrame, 0.f,
    15.f, 3.f
);

for (const FVector& Pos : Path)
{
    DrawDebugSphere(GetWorld(), Pos, 3.f, 6, FColor::Green, false, -1.f);
}

Version History

Introduced in: 4.15

Version	Status	Notes
5.6	stable	—

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