Hey everyone, I’m trying to create a custom Niagara Data Interface in UE5 for sampling wind data from a custom UWindVectorField class. I’ve followed all the usual steps, but the data interface is not showing up in the “Add User Parameter → Data Interface” dropdown in Niagara.
Basically, what I am trying to do is show my wind simulation field using Niagara particles like Peter Sikachev is doing in this Youtube video: https://youtu.be/HTlALlfz_T0?t=841
Here’s what I’ve done so far:
Created two files:
- NiagaraWindFieldDataInterface.h:
- NiagaraWindFieldDataInterface.cpp:
What these files include:
- NiagaraWindFieldDataInterface.h:
// Fill out your copyright notice in the Description page of Project Settings.
#pragma once
#include "CoreMinimal.h"
#include "NiagaraDataInterface.h"
#include "WindVectorField.h"
#include "NiagaraWindFieldDataInterface.generated.h"
UCLASS(EditInlineNew, BlueprintType, Category = "Wind", meta = (DisplayName = "Wind Field"))
class EMBERFLIGHT_API UNiagaraWindFieldDataInterface : public UNiagaraDataInterface
{
GENERATED_BODY()
public:
UFUNCTION(BlueprintCallable, Category="Wind")
FVector GetZeroWind() const { return FVector::ZeroVector; }
UNiagaraWindFieldDataInterface();
UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Wind")
TObjectPtr<UWindVectorField> WindField;
virtual void GetFunctions(TArray<FNiagaraFunctionSignature>& OutFunctions) override;
virtual void GetVMExternalFunction(const FVMExternalFunctionBindingInfo& BindingInfo, void* InstanceData, FVMExternalFunction& OutFunc) override;
virtual bool Equals(const UNiagaraDataInterface* Other) const override;
virtual bool CanExecuteOnTarget(ENiagaraSimTarget Target) const override;
};
- NiagaraWindFieldDataInterface.cpp:
// Fill out your copyright notice in the Description page of Project Settings.
#include "NiagaraWindFieldDataInterface.h"
#include "NiagaraTypes.h"
#include "NiagaraModule.h"
#include "NiagarafunctionLibrary.h"
#include "Modules/ModuleManager.h"
#define LOCTEXT_NAMESPACE "NiagaraWindFieldDI"
UNiagaraWindFieldDataInterface::UNiagaraWindFieldDataInterface() {}
struct FSampleWindAtLocation
{
static void Exec(FVectorVMExternalFunctionContext& Context, const UWindVectorField* WindField)
{
VectorVM::FUserPtrHandler<const UWindVectorField> FieldHandler(Context);
VectorVM::FExternalFuncInputHandler<float> X(Context);
VectorVM::FExternalFuncInputHandler<float> Y(Context);
VectorVM::FExternalFuncInputHandler<float> Z(Context);
VectorVM::FExternalFuncRegisterHandler<float> OutX(Context);
VectorVM::FExternalFuncRegisterHandler<float> OutY(Context);
VectorVM::FExternalFuncRegisterHandler<float> OutZ(Context);
for (int32 i = 0; i < Context.GetNumInstances(); ++i)
{
FVector WorldPos(X.GetAndAdvance(), Y.GetAndAdvance(), Z.GetAndAdvance());
FVector Velocity = WindField ? WindField->SampleWindAtPosition(WorldPos) : FVector::ZeroVector;
*OutX.GetDestAndAdvance() = Velocity.X;
*OutY.GetDestAndAdvance() = Velocity.Y;
*OutZ.GetDestAndAdvance() = Velocity.Z;
}
}
};
void UNiagaraWindFieldDataInterface::GetFunctions(TArray<FNiagaraFunctionSignature>& OutFunctions)
{
FNiagaraFunctionSignature Sig;
Sig.Name = FName(TEXT("SampleWindAtLocation"));
Sig.Inputs.Add(FNiagaraVariable(FNiagaraTypeDefinition(GetClass()), TEXT("Wind Field")));
Sig.Inputs.Add(FNiagaraVariable(FNiagaraTypeDefinition::GetFloatDef(), TEXT("X")));
Sig.Inputs.Add(FNiagaraVariable(FNiagaraTypeDefinition::GetFloatDef(), TEXT("Y")));
Sig.Inputs.Add(FNiagaraVariable(FNiagaraTypeDefinition::GetFloatDef(), TEXT("Z")));
Sig.Outputs.Add(FNiagaraVariable(FNiagaraTypeDefinition::GetFloatDef(), TEXT("OutX")));
Sig.Outputs.Add(FNiagaraVariable(FNiagaraTypeDefinition::GetFloatDef(), TEXT("OutY")));
Sig.Outputs.Add(FNiagaraVariable(FNiagaraTypeDefinition::GetFloatDef(), TEXT("OutZ")));
Sig.SetDescription(LOCTEXT("SampleWindDesc", "Sample wind velocity at a given world position"));
Sig.bMemberFunction = true;
OutFunctions.Add(Sig);
}
void UNiagaraWindFieldDataInterface::GetVMExternalFunction(const FVMExternalFunctionBindingInfo& BindingInfo, void* InstanceData, FVMExternalFunction& OutFunc)
{
if (BindingInfo.Name == TEXT("SampleWindAtLocation"))
{
OutFunc = FVMExternalFunction::CreateLambda([this](FVectorVMExternalFunctionContext& Context)
{
FSampleWindAtLocation::Exec(Context, WindField);
});
}
}
bool UNiagaraWindFieldDataInterface::Equals(const UNiagaraDataInterface* Other) const
{
const UNiagaraWindFieldDataInterface* OtherTyped = CastChecked<UNiagaraWindFieldDataInterface>(Other);
return OtherTyped && OtherTyped->WindField == WindField;
}
bool UNiagaraWindFieldDataInterface::CanExecuteOnTarget(ENiagaraSimTarget Target) const
{
return true;
}
#undef LOCTEXT_NAMESPACE
Some explanation for the code:
-
Added a dummy UFUNCTION (FVector GetZeroWind()) marked as BlueprintCallable, just to ensure it’s exposed for reflection.
-
The WindField is exposed via:
UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = “Wind”)
TObjectPtr WindField;
Just to be sure that the data interface is registered successfully, I have also tried to list it in the console upon begin play:
My_Game.cpp (this is the game module):
include "EmberFlight.h"
#include "NiagaraDataInterface.h"
#include "NiagaraWindFieldDataInterface.h"
#include "NiagaraDataInterface.h"
#include "UObject/UObjectIterator.h"
#include "Modules/ModuleManager.h"
IMPLEMENT_PRIMARY_GAME_MODULE( FDefaultGameModuleImpl, EmberFlight, "EmberFlight" );
void FEmberFlightModule::StartupModule()
{
UE_LOG(LogTemp, Warning, TEXT("Wind DI class is: %s"), *UNiagaraWindFieldDataInterface::StaticClass()->GetName());
}
void FEmberFlightModule::ShutdownModule()
{
}
void ListAllNiagaraInterfaces()
{
static const FName TempClassName = UNiagaraWindFieldDataInterface::StaticClass()->GetFName();
for (TObjectIterator<UClass> It; It; ++It)
{
if (It->IsChildOf(UNiagaraDataInterface::StaticClass()) && !It->HasAnyClassFlags(CLASS_Abstract))
{
UE_LOG(LogTemp, Warning, TEXT("Found DI: %s"), *It->GetName());
}
}
}
My_Game_GameMode.cpp:
// Copyright Epic Games, Inc. All Rights Reserved.
#include "EmberFlightGameMode.h"
#include "EmberFlight.h"
#include "UObject/ConstructorHelpers.h"
AEmberFlightGameMode::AEmberFlightGameMode()
{
// set default pawn class to our Blueprinted character
static ConstructorHelpers::FClassFinder<APawn> PlayerPawnBPClass(TEXT("Blueprint'/Game/Blueprints/BP_PhoenixCharacter.BP_PhoenixCharacter'"));
if (PlayerPawnBPClass.Class != NULL)
{
DefaultPawnClass = PlayerPawnBPClass.Class;
}
}
void AEmberFlightGameMode::BeginPlay()
{
Super::BeginPlay();
ListAllNiagaraInterfaces();
// Initialize Wind Field
WindFieldInstance = NewObject<UWindVectorField>(this);
if (WindFieldInstance)
{
WindFieldInstance->Initialize(30, 30, 30, 100.0f);
}
}
Console Log Image with registered wind field interface: https://imgur.com/a/16aRI24
Add User parameters → Data Interface → (custom wind field date interface not appearing): https://imgur.com/a/XJSe4K7