Simple Logic about replacing Material nodes in UE

AlterMaterialParameter.cpp

void AlterMaterialParameter_Simple(UMaterial* Mat)
{
	UTexture2DArrayFactory* Texture2DArrayFactory = NewObject<UTexture2DArrayFactory>();
	UTexture2DArray* DummyTex = Cast<UTexture2DArray>(Texture2DArrayFactory->FactoryCreateNew(UTexture2DArray::StaticClass(),Mat,NAME_None,RF_Standalone | RF_Transactional,nullptr,GWarn));
	TArray<UMaterialExpressionTextureSampleParameter* >  ParamsTextureSamples;
	for (int32 ExpressionIndex = 0; ExpressionIndex < Mat->Expressions.Num(); ExpressionIndex++)
	{
		auto* ExpressionPtr = Cast<UMaterialExpressionTextureSampleParameter>(Mat->Expressions[ExpressionIndex]);
		if (ExpressionPtr)
		{
			ParamsTextureSamples.Add(ExpressionPtr);
		}
	}
	
	if(ParamsTextureSamples.Num() == 0) {return;}
	for(int i = 0 ; i < ParamsTextureSamples.Num();i++)
	{
		auto TargetExpression = ParamsTextureSamples[i];
		if (!Mat->MaterialGraph)
		{
			Mat->MaterialGraph = CastChecked<UMaterialGraph>(FBlueprintEditorUtils::CreateNewGraph(Mat, NAME_None, UMaterialGraph::StaticClass(), UMaterialGraphSchema::StaticClass()));
			Mat->MaterialGraph->Material = Mat;
			Mat->MaterialGraph->RebuildGraph();
		}
	
		UMaterialGraphNode* GraphNode = Cast<UMaterialGraphNode>(TargetExpression->GraphNode);
		if(!GraphNode)
		{
			UE_LOG(LogTemp, Error, TEXT("No Graph Node"));
			return ;
		}


		UAssetEditorSubsystem* AssetEditorSubsystem = GEditor->GetEditorSubsystem<UAssetEditorSubsystem>();
		AssetEditorSubsystem->CloseAllEditorsForAsset( Mat );
	
		UMaterialExpression* TexCoordExpression = TargetExpression->Coordinates.Expression;
		UMaterialExpressionTextureSampleParameter2DArray* Tex2DArrayExpression=
			NewObject<UMaterialExpressionTextureSampleParameter2DArray>(Mat);
		Tex2DArrayExpression->ParameterName = *FString::Printf(TEXT("%s_Arr"),*TargetExpression->ParameterName.ToString());
		Tex2DArrayExpression->SamplerType = SAMPLERTYPE_Color;
		Tex2DArrayExpression->Group = TargetExpression->Group;
		Tex2DArrayExpression->Texture = DummyTex;
		Tex2DArrayExpression->MaterialExpressionEditorX = TargetExpression->MaterialExpressionEditorX;
		Tex2DArrayExpression->MaterialExpressionEditorY = TargetExpression->MaterialExpressionEditorY - 96;
		Mat->MaterialGraph->AddExpression(Tex2DArrayExpression,/*bUserInvoke*/ false);
		Mat->Expressions.Add(Tex2DArrayExpression);

		auto Tex2DArrayGraphNode = Cast<UMaterialGraphNode>(Tex2DArrayExpression->GraphNode);

		Tex2DArrayGraphNode->ReplaceNode(GraphNode);
		TArray<UEdGraphPin*> Tex2DArrayGraphInputPins;
		Tex2DArrayGraphNode->GetInputPins(Tex2DArrayGraphInputPins);
		GraphNode->GetGraph()->GetSchema()->BreakPinLinks(*Tex2DArrayGraphInputPins[0],true);
		
		GraphNode->GetGraph()->GetSchema()->BreakNodeLinks(*GraphNode);
		Mat->MaterialGraph->LinkMaterialExpressionsFromGraph();
		
		auto * LayerExpression= Cast<UMaterialExpressionConstant>(UMaterialEditingLibrary::CreateMaterialExpression(Mat,UMaterialExpressionConstant::StaticClass()));
		LayerExpression->R = 0.0;

		FString FunctionString = TEXT("/Engine/Functions/Engine_MaterialFunctions02/Utility/BreakOutFloat2Components.BreakOutFloat2Components");
		UMaterialFunction*  BreakOutFloat2 = LoadObject<UMaterialFunction>(nullptr, *FunctionString, nullptr, LOAD_None, nullptr);
		UMaterialExpressionMaterialFunctionCall* BreakOutFloat2Expression=
			Cast<UMaterialExpressionMaterialFunctionCall>(UMaterialEditingLibrary::CreateMaterialExpression(Mat,UMaterialExpressionMaterialFunctionCall::StaticClass()));
		BreakOutFloat2Expression->MaterialFunction = BreakOutFloat2;
		BreakOutFloat2Expression->UpdateFromFunctionResource();

		TexCoordExpression->ConnectExpression(BreakOutFloat2Expression->GetInput(0),0);
		
		FunctionString = TEXT("/Engine/Functions/Engine_MaterialFunctions02/Utility/MakeFloat3.MakeFloat3");
		UMaterialFunction*  MakeFloat3= LoadObject<UMaterialFunction>(nullptr, *FunctionString, nullptr, LOAD_None, nullptr);
		UMaterialExpressionMaterialFunctionCall* MakeFloat3Expression =
			Cast<UMaterialExpressionMaterialFunctionCall>(UMaterialEditingLibrary::CreateMaterialExpression(Mat,UMaterialExpressionMaterialFunctionCall::StaticClass()));
		MakeFloat3Expression->MaterialFunction = MakeFloat3;
		MakeFloat3Expression->UpdateFromFunctionResource();

		BreakOutFloat2Expression->ConnectExpression(MakeFloat3Expression->GetInput(0),0); // u
		BreakOutFloat2Expression->ConnectExpression(MakeFloat3Expression->GetInput(1),1); // v
		LayerExpression->ConnectExpression(MakeFloat3Expression->GetInput(2),0); // w

		MakeFloat3Expression->ConnectExpression(&(Tex2DArrayExpression->Coordinates),0); // uvw
		
		Mat->Expressions.Remove(GraphNode->MaterialExpression);
		Mat->RemoveExpressionParameter(GraphNode->MaterialExpression);
		
		Mat->MaterialGraph->RebuildGraph();
	}	
	Mat->MarkPackageDirty();
	Mat->PostEditChange();
}