Set Niagara Variable (Audio Player) doesn't exist ?

Development Programming & Scripting Blueprint
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1

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I am trying to trigger bullet casing sounds within the Niagara system for bullet shells ejected. I currently feed the static mesh information from the weapon data via “SetNiagaraVariable(StaticMesh).” I want to do the same for the sound to play, which has the type AudioPlayer. How do I make it and what node do I use to set it?

2

Bump…

Is this just not a thing in BP? Can it even be done with C++. Seems odd to have a one-shot audio playing capability and not be able to set it programmatically at runtime.

3

Hi, it is possible to set this at runtime, however this functionality isn’t exposed out of the box to Blueprints. You can however create a simple C++ function in a Blueprint library. A quick example inspired by functions in NiagaraFunctionLibrary would look like this:

Create a UNiagaraExtendedFunctionLibrary class derived from UBlueprintFunctionLibrary

In UNiagaraExtendedFunctionLibrary.h:

/** Sets the sound to play properties on an audio player data interface, this is destructive as it modifies the data interface. */
	UFUNCTION(BlueprintCallable, Category = "Niagara", meta = (DisplayName = "Set Niagara Audio Player Properties"))
	static void OverrideSystemUserVariableAudioPlayer(UNiagaraComponent* NiagaraSystem, const FString& OverrideName, USoundBase* SoundToPlay, USoundAttenuation* SoundAttenuation, USoundConcurrency* SoundConcurrency);

In UNiagaraExtendedFunctionLibrary.cpp:

#include "NiagaraComponent.h"
#include "NiagaraDataInterfaceAudioPlayer.h"

void UNiagaraExtendedFunctionLibrary::OverrideSystemUserVariableAudioPlayer(UNiagaraComponent* NiagaraSystem, const FString& OverrideName, USoundBase* SoundToPlay, USoundAttenuation* SoundAttenuation, USoundConcurrency* SoundConcurrency)
{
	if (!NiagaraSystem)
	{
		UE_LOG(LogTemp, Warning, TEXT("NiagaraSystem in \"Override System User Variable Audio Player\" is NULL, OverrideName \"%s\", skipping."), *OverrideName);
		return;
	}
	
	const FNiagaraParameterStore& OverrideParameters = NiagaraSystem->GetOverrideParameters();
	FNiagaraVariable Variable(FNiagaraTypeDefinition(UNiagaraDataInterfaceAudioPlayer::StaticClass()), *OverrideName);

	const int32 Index = OverrideParameters.IndexOf(Variable);
	if (Index == INDEX_NONE)
	{
		UE_LOG(LogTemp, Warning, TEXT("UNiagaraExtendedFunctionLibrary::OverrideSystemUserVariableAudioPlayer: Did not find a matching Audio Player Data Interface variable named \"%s\" in the User variables of NiagaraSystem \"%s\"."), *OverrideName, *GetFullNameSafe(NiagaraSystem));
		return;
	}
	
	UNiagaraDataInterfaceAudioPlayer* AudioPlayerInterface = Cast<UNiagaraDataInterfaceAudioPlayer>(OverrideParameters.GetDataInterface(Index));

	AudioPlayerInterface->SoundToPlay = SoundToPlay;
	AudioPlayerInterface->Attenuation = SoundAttenuation;
	AudioPlayerInterface->Concurrency = SoundConcurrency;
}

And don’t forget to add “Niagara” into the PrivateDependencyModuleNames in your .Build.cs file.

After that you can call the node in Blueprint with your variable name:

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