【Unreal Engine 4】動的にUE4 ナイアガラエミッターのマテリアルを変更するモジュール作成事例

// ナイアガラ用 汎用マテリアル切り替え
UCLASS(EditInlineNew,meta = (DisplayName = "Test Change Material"), Blueprintable, BlueprintType)
class UTestNiagaraDataInterfaceChangeMaterial : public UNiagaraDataInterface
{
	GENERATED_BODY()
public:
	// 実行時用のインスタンスパラメータ
	struct FPerInstanceData
	{
		void Update(UTestNiagaraDataInterfaceChangeMaterial* Parent, FNiagaraSystemInstance* SystemInstance, float DeltaSeconds);
		void SetMaterial(UTestNiagaraDataInterfaceChangeMaterial* Parent, FNiagaraSystemInstance* SystemInstance, const int32 SwitchIndex);

		int32 prevSwitchIndex_ = -1;
	};

	// コンストラクタ
	UTestNiagaraDataInterfaceChangeMaterial(const FObjectInitializer& ObjectInitializer);

	virtual void PostInitProperties() override;
	virtual bool InitPerInstanceData(void* PerInstanceData, FNiagaraSystemInstance* InSystemInstance) override;
	virtual void DestroyPerInstanceData(void* PerInstanceData, FNiagaraSystemInstance* InSystemInstance) override {}
	virtual bool PerInstanceTick(void* PerInstanceData, FNiagaraSystemInstance* SystemInstance, float DeltaSeconds) override;
	virtual int32 PerInstanceDataSize() const override { return sizeof(FPerInstanceData); }
	virtual bool Equals(const UNiagaraDataInterface* Other) const override;
	virtual bool HasPreSimulateTick() const { return true; }

	// 切替マテリアル値の変更
	void SetSwitchIndex(const int32 SwitchIndex) { switchIndex_ = SwitchIndex; }

protected:
	virtual bool CopyToInternal(UNiagaraDataInterface* Destination) const override;

protected:

	// 切替マテリアル値
	UPROPERTY(EditAnywhere)
	int32 switchIndex_ = 0;
	// 切替先マテリアルの参照を設定
	UPROPERTY(EditAnywhere)
	FNiagaraUserParameterBinding materialVariable_;
	// 切替マテリアル配列
	UPROPERTY(EditAnywhere)
	TArray changeMaterials_;
};

UTestNiagaraDataInterfaceChangeMaterial::UTestNiagaraDataInterfaceChangeMaterial(const FObjectInitializer& ObjectInitializer)
	: Super(ObjectInitializer)
{
	// エディタ上での設定方法をマテリアルインターフェイスタイプにします
	FNiagaraTypeDefinition MaterialDef(UMaterialInterface::StaticClass());
	materialVariable_.Parameter.SetType(MaterialDef);
}

void UTestNiagaraDataInterfaceChangeMaterial::PostInitProperties()
{
	// 型としてNiagaraに登録します
	Super::PostInitProperties();
	if (HasAnyFlags(RF_ClassDefaultObject))
	{
		FNiagaraTypeRegistry::Register(FNiagaraTypeDefinition(GetClass()), true, false, false);
	}
}


bool UTestNiagaraDataInterfaceChangeMaterial::InitPerInstanceData(void* PerInstanceData, FNiagaraSystemInstance* InSystemInstance)
{
	auto* piData = new (PerInstanceData) FPerInstanceData;
	return true;
}


bool UTestNiagaraDataInterfaceChangeMaterial::CopyToInternal(UNiagaraDataInterface* Destination) const
{
	if (!Super::CopyToInternal(Destination)) { return false; }
	// この関数の実装がないとUE4Editor上で変更したパラメータがランタイム中に反映されないので注意！
	if (auto* dest = Cast<UTestNiagaraDataInterfaceChangeMaterial>(Destination))
	{
		dest->switchIndex_ = switchIndex_;
		dest->materialVariable_ = materialVariable_;
		dest->changeMaterials_ = changeMaterials_;
		return true;
	}

	return false;
}

bool UTestNiagaraDataInterfaceChangeMaterial::Equals(const UNiagaraDataInterface* Other) const
{
	if (!Super::Equals(Other)) { return false; }

	if (auto* changeMaterial = Cast<UTestNiagaraDataInterfaceChangeMaterial>(Other))
	{
		return changeMaterial->switchIndex_ == switchIndex_ &&
			changeMaterial->materialVariable_ == materialVariable_ &&
			changeMaterial->changeMaterials_ == changeMaterials_;
	}

	return false;
}

bool UTestNiagaraDataInterfaceChangeMaterial::PerInstanceTick(void* PerInstanceData, FNiagaraSystemInstance* SystemInstance, float DeltaSeconds)
{
	check(PerInstanceData);
	check(SystemInstance);

	auto* piData = static_cast<FPerInstanceData*>(PerInstanceData);
	piData->Update(this, SystemInstance, DeltaSeconds);
	return false;
}

void UTestNiagaraDataInterfaceChangeMaterial::FPerInstanceData::Update(UTestNiagaraDataInterfaceChangeMaterial* Parent, FNiagaraSystemInstance* SystemInstance, float DeltaSeconds)
{
	if (Parent != nullptr && Parent->materialVariable_.Parameter.IsValid())
	{
		if (auto* niagaraComponent = Cast<UNiagaraComponent>(SystemInstance->GetAttachComponent()))
		{
			if (Parent->switchIndex_ != prevSwitchIndex_)
			{
				SetMaterial(Parent, SystemInstance, Parent->switchIndex_);
				prevSwitchIndex_ = Parent->switchIndex_;
			}
		}
	}
}

void UTestNiagaraDataInterfaceChangeMaterial::FPerInstanceData::SetMaterial(UTestNiagaraDataInterfaceChangeMaterial* Parent, FNiagaraSystemInstance* SystemInstance, const int32 SwitchIndex)
{
	if (Parent != nullptr && SystemInstance != nullptr)
	{
		// マテリアル差し替え
		if (auto* niagaraComponent = Cast<UNiagaraComponent>(SystemInstance->GetAttachComponent()))
		{
			UMaterialInterface* changeMaterial = nullptr;
			if (SwitchIndex < Parent->changeMaterials_.Num())
			{
				changeMaterial = Parent->changeMaterials_[SwitchIndex];
			}
			if (changeMaterial)
			{
				niagaraComponent->SetVariableMaterial(Parent->materialVariable_.Parameter.GetName(), changeMaterial);
			}
		}
	}
}

const FNiagaraParameterStore& overrideParameters = NiagaraComponent->GetOverrideParameters();

		// 例えばスプライトのマテリアル変更
		{
			FNiagaraVariable Variable(FNiagaraTypeDefinition(UTestNiagaraDataInterfaceChangeMaterial::StaticClass()), TEXT("ChangeSpriteMaterial"));
			int32 index = overrideParameters.IndexOf(Variable);
			if (index != INDEX_NONE)
			{
				if (UTestNiagaraDataInterfaceChangeMaterial* changeMaterialInterface = Cast<UTestNiagaraDataInterfaceChangeMaterial>(overrideParameters.GetDataInterface(index)))
				{
					changeMaterialInterface->SetSwitchIndex(SwitchIndex);
				}
			}
		}
		// 例えばメッシュのマテリアル変更
		{
			FNiagaraVariable Variable(FNiagaraTypeDefinition(UTestNiagaraDataInterfaceChangeMaterial::StaticClass()), TEXT("ChangeMeshMaterial"));
			int32 index = overrideParameters.IndexOf(Variable);
			if (index != INDEX_NONE)
			{
				if (UTestNiagaraDataInterfaceChangeMaterial* changeMaterialInterface = Cast<UTestNiagaraDataInterfaceChangeMaterial>(overrideParameters.GetDataInterface(index)))
				{
					changeMaterialInterface->SetSwitchIndex(SwitchIndex);
				}
			}
		}