76 lines
2.3 KiB
Markdown
76 lines
2.3 KiB
Markdown
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# MaterialControlFlow
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- **功能描述：** 标识该UMaterialExpression为一个控制流节点，当前在材质蓝图右键菜单中隐藏。
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- **使用位置：** UCLASS
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- **引擎模块：** Material
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- **元数据类型：** bool
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- **限制类型：** UMaterialExpression子类
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- **常用程度：** ★
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标识该UMaterialExpression为一个控制流节点，当前在材质蓝图右键菜单中隐藏。
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一般是在IfThenElse，ForLoop这种节点上，当前引擎实现还未完善，因此该功能禁用。
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## 源码例子：
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```cpp
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UCLASS(collapsecategories, hidecategories=Object, MinimalAPI)
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class UMaterialExpressionIf : public UMaterialExpression
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{}
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UCLASS(collapsecategories, hidecategories = Object, MinimalAPI, meta=(MaterialControlFlow))
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class UMaterialExpressionIfThenElse : public UMaterialExpression
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{}
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```
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## 测试效果：
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可以找到If节点，但是无法调用IfThenElse节点。
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## 原理：
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在遍历所有可用FMaterialExpression的时候，如果有MaterialControlFlow则略过。当前引擎下AllowMaterialControlFlow一直未false，未实现。
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```cpp
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// r.MaterialEnableControlFlow is removed and the feature is forced disabled as how control flow should be
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// implemented in the material editor is still under discussion.
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inline bool AllowMaterialControlFlow()
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{
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return false;
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}
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void MaterialExpressionClasses::InitMaterialExpressionClasses()
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{
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static const auto CVarMaterialEnableNewHLSLGenerator = IConsoleManager::Get().FindTConsoleVariableDataInt(TEXT("r.MaterialEnableNewHLSLGenerator"));
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const bool bEnableControlFlow = AllowMaterialControlFlow();
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const bool bEnableNewHLSLGenerator = CVarMaterialEnableNewHLSLGenerator->GetValueOnAnyThread() != 0;
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for( TObjectIterator<UClass> It ; It ; ++It )
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{
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if( Class->IsChildOf(UMaterialExpression::StaticClass()) )
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{
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// Hide node types related to control flow, unless it's enabled
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if (!bEnableControlFlow && Class->HasMetaData("MaterialControlFlow"))
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{
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continue;
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}
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if (!bEnableNewHLSLGenerator && Class->HasMetaData("MaterialNewHLSLGenerator"))
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{
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continue;
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}
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// Hide node types that are tagged private
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if(Class->HasMetaData(TEXT("Private")))
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{
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continue;
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}
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AllExpressionClasses.Add(MaterialExpression);
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}
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}
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}
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```
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