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03-UnrealEngine/Gameplay/UObject/UnrealSpecifiers/Meta/Niagara/NiagaraClearEachFrame.md

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+# NiagaraClearEachFrame
+
+- **功能描述：** ScriptStruct /Script/Niagara.NiagaraSpawnInfo
+- **使用位置：** USTRUCT
+- **引擎模块：** Niagara
+- **元数据类型：** bool
+- **常用程度：** 0
+
+指定某结构的数据在Niagara后续每一帧不应该读取，只作为初始数据。
+
+当前只用在FNiagaraSpawnInfo上，仅仅内部用。
+
+## 源码例子：
+
+```cpp
+/** Data controlling the spawning of particles */
+USTRUCT(BlueprintType, meta = (DisplayName = "Spawn Info", NiagaraClearEachFrame = "true"))
+struct FNiagaraSpawnInfo
+{
+}
+```
+
+## 原理：
+
+```cpp
+// If the NiagaraClearEachFrame value is set on the data set, we don't bother reading it in each frame as we know that it is is invalid. However,
+// this is only used for the base data set. Other reads are potentially from events and are therefore perfectly valid.
+if (DataSetIndex == 0 && Var.GetType().GetScriptStruct() != nullptr && Var.GetType().GetScriptStruct()->GetMetaData(TEXT("NiagaraClearEachFrame")).Equals(TEXT("true"), ESearchCase::IgnoreCase))
+{
+	Fmt = VariableName + TEXT("{0} = {4};\n");
+}
+```

03-UnrealEngine/Gameplay/UObject/UnrealSpecifiers/Meta/Niagara/NiagaraInternalType.md

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+# NiagaraInternalType
+
+- **功能描述：** 指定该结构的类型为Niagara的内部类型。
+- **使用位置：** USTRUCT
+- **引擎模块：** Niagara
+- **元数据类型：** bool
+- **常用程度：** 0
+
+指定该结构的类型为Niagara的内部类型。
+
+用来和用户自定义的类型区分。用户不需要自己使用该元数据。
+
+## 源码例子：
+
+```cpp
+USTRUCT(meta = (DisplayName = "Half", NiagaraInternalType = "true"))
+struct FNiagaraHalf
+{
+	GENERATED_USTRUCT_BODY()
+
+	UPROPERTY(EditAnywhere, Category = Parameters)
+	uint16 Value = 0;
+};
+
+USTRUCT(meta = (DisplayName = "Half Vector2", NiagaraInternalType = "true"))
+struct FNiagaraHalfVector2
+{
+	GENERATED_USTRUCT_BODY()
+
+	UPROPERTY(EditAnywhere, Category = Parameters)
+	uint16 x = 0;
+
+	UPROPERTY(EditAnywhere, Category = Parameters)
+	uint16 y = 0;
+};
+
+USTRUCT(meta = (DisplayName = "Half Vector3", NiagaraInternalType = "true"))
+struct FNiagaraHalfVector3
+{
+	GENERATED_USTRUCT_BODY()
+
+	UPROPERTY(EditAnywhere, Category = Parameters)
+	uint16 x = 0;
+
+	UPROPERTY(EditAnywhere, Category = Parameters)
+	uint16 y = 0;
+
+	UPROPERTY(EditAnywhere, Category = Parameters)
+	uint16 z = 0;
+};
+
+USTRUCT(meta = (DisplayName = "Half Vector4", NiagaraInternalType = "true"))
+struct FNiagaraHalfVector4
+{
+	GENERATED_USTRUCT_BODY()
+
+	UPROPERTY(EditAnywhere, Category = Parameters)
+	uint16 x = 0;
+
+	UPROPERTY(EditAnywhere, Category = Parameters)
+	uint16 y = 0;
+
+	UPROPERTY(EditAnywhere, Category = Parameters)
+	uint16 z = 0;
+
+	UPROPERTY(EditAnywhere, Category = Parameters)
+	uint16 w = 0;
+};
+
+```
+
+## 原理：
+
+```cpp
+#if WITH_EDITORONLY_DATA
+bool FNiagaraTypeDefinition::IsInternalType() const
+{
+	if (const UScriptStruct* ScriptStruct = GetScriptStruct())
+	{
+		return ScriptStruct->GetBoolMetaData(TEXT("NiagaraInternalType"));
+	}
+
+	return false;
+}
+#endif
+```