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Controlling FMOD Parameters in Unreal Engine 4

In this tutorial we will control FMOD Game Parameters by using Blueprint nodes and by writing simple C++ code.

Preparation in FMOD Studio

Create a new Event in FMOD Studio and insert a Continuous Parameter named Pitch with values that range between -12 and 12 (map it accordingly to the master pitch setting):

FMOD Studio Event with Pitch Parameter
FMOD Studio Event with Pitch Parameter

Also create a Global Parameter named EQ Global with values that range between 0 and 1. Add an automation curve, so that the frequency of the filter goes down when reaching the value 1:

FMOD Studio Event with Global Parameter
FMOD Studio Event with Global Parameter

Build the banks and switch over to the Unreal Editor.

Controlling FMOD Parameters by using Blueprints

We can use the Event Instance Set Parameter node to control a Parameter of an Event Instance in Blueprints:

FMOD Event Instance Set Parameter node
FMOD Event Instance Set Parameter node

Here we are playing the Event by pressing the 1 key. We check every frame if the Event Instance is valid, and if it is, we set the Parameter to a new pitch variable (remember to make the variable instance editable). You will be able to modify the parameter value in the details tab of the Actor when playing the game.

If you are using the FMOD Ambient Sound Actor or the FMODAudio component instead, you can simply reference the FMODAudio component and use the Set Parameter node:

FMODAudio Set Parameter node
FMODAudio Set Parameter node

Controlling FMOD Global Parameters by using Blueprints

Use the Set Global Parameter By Name node to control Global Parameters in a Blueprint:

FMOD Set Global Parameter By Name node
FMOD Set Global Parameter By Name node

We extended the previous Blueprint to include the Set Global Parameter by Name node and created a new float variable named EQ that we attached to the Value field. Start the level and change the values in the Details tab of your Character/Actor

Controlling FMOD Parameters in UE4 by writing C++ code

In this tutorial section, we will take a look at how to control FMOD Parameters by interfacing with the Blueprint functions or directly accessing FMOD’s Studio API.

EventInstanceSetParameter and setParameterByName

Declare a float variable called pitch:

UPROPERTY(EditAnywhere, Category = "FMOD", meta = (ClampMin = "-12", ClampMax = "12"))
float Pitch;

The pitch variable will show up in the Details tab of our Actor thanks to the EditAnywhere specifier. ClampMin and ClampMax allow us to visually restrict the range of the variable value:

FMOD Event Parameter in the Details tab
FMOD Event Parameter in the Details tab

We can now call EventInstanceSetParameter to set the Parameter to our Pitch variable:

if (UFMODBlueprintStatics::EventInstanceIsValid(InstanceWrapper))
{		
	UFMODBlueprintStatics::EventInstanceSetParameter(InstanceWrapper, FName("Pitch"), Pitch);
}

Alternatively, it is possible to directly change the Parameter by using FMOD’s Studio API:

InstanceWrapper.Instance->setParameterByName(TCHAR_TO_UTF8(*FName("Pitch").ToString()), Pitch);

setParameterByID

In the Character’s header file, declare a FMOD_STUDIO_PARAMETER_ID variable:

FMOD_STUDIO_PARAMETER_ID PitchParameterId;

We can retrieve the Parameter Id by getting the Event Description of the Event Instance, after that declaring a Parameter Description variable and getting the Parameter Description by calling the getParameterDescriptionByName function. We assign the Id of the Parameter Description to the Parameter Id variable we declared in the header file:

FMOD::Studio::EventDescription* eD;
InstanceWrapper.Instance->getDescription(&eD);
FMOD_STUDIO_PARAMETER_DESCRIPTION pD;
eD->getParameterDescriptionByName(TCHAR_TO_UTF8(*FString("Pitch")), &pD);
PitchParameterId = pD.id;

Alternatively, we can use the IFMODStudioModule singleton to get the Event Description from an UFMODEvent:

FMOD::Studio::EventDescription* eD = IFMODStudioModule::Get().GetEventDescription(Event, EFMODSystemContext::Max);
FMOD_STUDIO_PARAMETER_DESCRIPTION pD;
eD->getParameterDescriptionByName(TCHAR_TO_UTF8(*FString("Pitch")), &pD);
PitchParameterId = pD.id;

Setting a FMOD Global Parameter in C++

Let’s create a new float variable in our header file first:

UPROPERTY(EditAnywhere, Category = "FMOD", meta = (ClampMin = "0", ClampMax = "1"))
float EQ;

This variable will also be visible in the Editor. After that, we can set a Global Parameter by calling SetGlobalParameterByName in the Character’s class:

UFMODBlueprintStatics::SetGlobalParameterByName(FName("EQ Global"), EQ);

Insert the code above in the Tick function and start the game. By moving the EQ slider in the Character’s Detail tab, you will hear the parameter change taking place.

Congratulations! You learned how to control FMOD Parameters in Unreal Engine 4. In the next tutorial we will take a look at FMOD’s Mixer.

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