Why is my UNiagaraComponent null when using UNiagaraFunctionLibrary::SpawnSystemAttached

Development Programming & Scripting C++
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1

Hello community,

I’m trying to spawn projectiles that contain both Meshes and NiagaraSystems, I have a DataAsset that contains the relevant classes and properties for the spawning projectile which provides the variables via the parameter NewParams(using FProjectileParams struct).

When I spawn said projectile, the StaticMesh works fine, when I try to spawn the NiagaraSystem the function UNiagaraFunctionLibrary::SpawnSystemAttachedalways returns null and no effect appears.

Please see the code below:

void AProjectileBase::SetProjectileParams(const FProjectileParams& NewParams)
{
	if (IsValid(NewParams.ProjectileEffect))
	{
		GEngine->AddOnScreenDebugMessage(-1, 5.f, FColor::Yellow,
		                                 FString::Printf(
			                                 TEXT("%s() Creating Niagara System, System='%s'"), *FString(__FUNCTION__),
			                                 *NewParams.ProjectileEffect->GetName()
			                                 ));
		
		// const UNiagaraComponent* NiagaraComp = UNiagaraFunctionLibrary::SpawnSystemAttached(
		// 	NewParams.ProjectileEffect,
		// 	MeshComponent,
		// 	NAME_None,
		// 	FVector(0.f),
		// 	FRotator(0.f),
		// 	EAttachLocation::Type::KeepRelativeOffset,
		// 	true);
		
		const UNiagaraComponent* NiagaraComp = UNiagaraFunctionLibrary::SpawnSystemAtLocation(
			GetWorld(),
			NewParams.ProjectileEffect,
			MeshComponent->GetComponentLocation(),
			MeshComponent->GetComponentRotation(),
			NewParams.Scale,
			false);
		
		// ParticleSystemComponent = NiagaraComp;

		if (IsValid(NiagaraComp))
		{
			// Set scale
			if (!NewParams.Scale.IsZero())
			{
				ParticleSystemComponent->SetRelativeScale3D(NewParams.Scale);
			}
		}
	}

	if (IsValid(MeshComponent) && IsValid(NewParams.ProjectileMesh))
	{
		MeshComponent->SetStaticMesh(NewParams.ProjectileMesh);
	}

	if (IsValid(ProjectileMovementComponent))
	{
		ProjectileMovementComponent->InitialSpeed = NewParams.Speed;
		ProjectileMovementComponent->MaxSpeed = NewParams.Speed;
		ProjectileMovementComponent->ProjectileGravityScale = NewParams.Gravity;
		ProjectileMovementComponent->bShouldBounce = NewParams.bShouldBounce;
		ProjectileMovementComponent->Bounciness = NewParams.Bounciness;
	}
}

From the commented-out section, you can see I’ve tried both SpawnSystemAttached and SpawnSystemAtLocation - neither return a resulting UNiagaraComponent and without the following IsValidthe engine crashes.

The DebugMessage does in fact show the System is correct and when I pause the debugger I can see all objects are not nullptrs.

This is for a multiplayer game using GAS to trigger the ability that spawns these projectiles.

Unreal Engine 5.5.4

// Header file for ProjectileBase
{
	GENERATED_BODY()

public:
	AProjectileBase();

	void SetProjectileParams(const FProjectileParams &NewParams);

protected:
	UPROPERTY()
	TObjectPtr<class UProjectileMovementComponent> ProjectileMovementComponent;
	UPROPERTY()
	TObjectPtr<class UNiagaraComponent> ParticleSystemComponent;
	UPROPERTY()
	TObjectPtr<class UStaticMeshComponent> MeshComponent;
};


// FProjectileParams struct
struct FProjectileParams
{
	GENERATED_BODY()

	UPROPERTY(EditDefaultsOnly, Category = "Projectile")
	TSubclassOf<AProjectileBase> ProjectileClass;

	UPROPERTY(EditDefaultsOnly, Category = "Projectile")
	TObjectPtr<UStaticMesh> ProjectileMesh;

	UPROPERTY(EditDefaultsOnly, Category = "Projectile")
	TObjectPtr<UNiagaraSystem> ProjectileEffect;

	UPROPERTY(EditDefaultsOnly, Category = "Projectile")
	TObjectPtr<UShapeComponent> Collider;

	UPROPERTY(EditDefaultsOnly, Category = "Projectile")
	FVector Scale;

	UPROPERTY(EditDefaultsOnly, Category = "Projectile")
	float Speed = 1000.0f;

	UPROPERTY(EditDefaultsOnly, Category = "Projectile")
	float Gravity = .5f;

	UPROPERTY(EditDefaultsOnly, Category = "Projectile")
	float Range = 2000.0f;

	UPROPERTY(EditDefaultsOnly, Category = "Projectile")
	bool bShouldBounce = false;

	UPROPERTY(EditDefaultsOnly, Category = "Projectile")
	float Bounciness = 0.6f;
};

Any help would be greatly appreciated.

Thanks!

2

Double check your Niagara System asset is set up and passed correctly. Another possibility is it’s set up with culling that pre-culls the system.

Use your debugger to step INTO the SpawnSystemAttached down into the SpawnSystemAttachedWithParams and see exactly where it is bailing out and returning your null.