Working on MI SetParameter

Integration.code-workspace.tpl.json

@@ -63,10 +63,7 @@
     "extensions": {
         "recommendations": [
             "llvm-vs-code-extensions.vscode-clangd",
-            "vadimcn.vscode-lldb",
-            "dfarley1.file-picker",
-            "ms-python.python",
-            "ms-vscode.mono-debug"
+            "vadimcn.vscode-lldb"
         ]
     },
     "tasks": {

Plugins/BlueprintMCP/Source/BlueprintMCP/BlueprintMCP.Build.cs

@@ -29,7 +29,9 @@ public class BlueprintMCP : ModuleRules
 			"MaterialEditor",
 			"AnimGraph",
 			"AnimGraphRuntime",
-			"RHI"
+			"RHI",
+			"Slate",
+			"SlateCore"
 		});
 	}
 }

Plugins/BlueprintMCP/Source/BlueprintMCP/Handlers/MaterialInstance_DumpParameters.h

@@ -12,7 +12,7 @@
 #include "Materials/MaterialExpressionTextureSampleParameter2D.h"
 #include "Materials/MaterialExpressionStaticSwitchParameter.h"
 #include "Engine/Texture.h"
-#include "Material_DumpInstanceParameters.generated.h"
+#include "MaterialInstance_DumpParameters.generated.h"
 
 
 // ---------------------------------------------------------------------------
@@ -20,7 +20,7 @@
 // ---------------------------------------------------------------------------
 
 UCLASS()
-class UMCP_Material_DumpInstanceParameters : public UObject, public IMCPHandler
+class UMCP_MaterialInstance_DumpParameters : public UObject, public IMCPHandler
 {
 	GENERATED_BODY()
 

Plugins/BlueprintMCP/Source/BlueprintMCP/Handlers/MaterialInstance_SetParameter.h

@@ -0,0 +1,110 @@
+#pragma once
+
+#include "CoreMinimal.h"
+#include "MCPHandler.h"
+#include "MCPFetcher.h"
+#include "MCPUtils.h"
+#include "Materials/MaterialInstanceConstant.h"
+#include "Misc/DefaultValueHelper.h"
+#include "MaterialInstance_SetParameter.generated.h"
+
+
+// ---------------------------------------------------------------------------
+// ---------------------------------------------------------------------------
+// ---------------------------------------------------------------------------
+
+UCLASS()
+class UMCP_MaterialInstance_SetParameter : public UObject, public IMCPHandler
+{
+	GENERATED_BODY()
+
+public:
+	UPROPERTY(meta=(Description="Material Instance path"))
+	FString Path;
+
+	UPROPERTY(meta=(Description="Parameter name to set"))
+	FString Parameter;
+
+	UPROPERTY(meta=(Description="Value to set (uses Unreal text format, e.g. '0.5' for scalar, '(R=1,G=0,B=0,A=1)' for vector)"))
+	FString Value;
+
+	virtual FString GetDescription() const override
+	{
+		return TEXT("Set a parameter override on a Material Instance.");
+	}
+
+	virtual void Handle(const FJsonObject* Json, FStringBuilderBase& Result) override
+	{
+		MCPFetcher F(Result);
+		UMaterialInstanceConstant* MI = F.Asset(Path).Cast<UMaterialInstanceConstant>();
+		if (!MI) return;
+
+		auto Parameters = MCPUtils::MaterialParameters(MI);
+
+		// Find a parameter with a matching name.
+		FName Name(*Parameter);
+		MCPMaterialParameter* Found = nullptr;
+		int MatchCount = 0;
+		for (auto& P : Parameters)
+		{
+			if (P.Name == Name)
+			{
+				MatchCount++;
+				Found = &P;
+			}
+		}
+		if (MatchCount > 1)
+		{
+			Result.Appendf(TEXT("More than one parameter named '%s'"), *Parameter);
+			return;
+		}
+		if (MatchCount == 0)
+		{
+			Result.Appendf(TEXT("No parameter named '%s'"), *Parameter);
+			return;
+		}
+		if (Found->Metadata.PrimitiveDataIndex != INDEX_NONE)
+		{
+			Result.Appendf(TEXT("Parameter '%s' uses custom primitive data and cannot be set on a material instance"), *Parameter);
+			return;
+		}
+
+		FMaterialParameterInfo Info(*Parameter);
+		EMaterialParameterType Type = Found->Metadata.Value.Type;
+
+		F.PreEdit();
+		switch (Type)
+		{
+		case EMaterialParameterType::Scalar:
+		{
+			float ScalarValue;
+			if (!FDefaultValueHelper::ParseFloat(Value, ScalarValue))
+			{
+				Result.Appendf(TEXT("Failed to parse '%s' as a float"), *Value);
+				return;
+			}
+			MI->SetScalarParameterValueEditorOnly(Info, ScalarValue);
+			break;
+		}
+		case EMaterialParameterType::Vector:
+		{
+			FLinearColor Color;
+			if (!Color.InitFromString(Value))
+			{
+				Result.Appendf(TEXT("Failed to parse '%s' as a color/vector (expected format: '(R=1,G=0,B=0,A=1)')"), *Value);
+				return;
+			}
+			MI->SetVectorParameterValueEditorOnly(Info, Color);
+			break;
+		}
+		default:
+			Result.Appendf(TEXT("Unsupported parameter type for '%s'"), *Parameter);
+			return;
+		}
+		F.PostEdit();
+		MCPUtils::SaveGenericPackage(MI);
+
+		Result.Appendf(TEXT("Set '%s' = %s on %s\n"),
+			*Parameter, *Value, *MCPUtils::FormatName(MI));
+	}
+};

Plugins/BlueprintMCP/Source/BlueprintMCP/Private/MCPFetcher.cpp

@@ -48,7 +48,6 @@ MCPFetcher& MCPFetcher::Walk(const FString& Path)
 {
 	if (bError) return *this;
 
-	// Split on commas
 	TArray<FString> Segments;
 	Path.ParseIntoArray(Segments, TEXT(","));
 	if (Segments.Num() == 0)
@@ -57,46 +56,33 @@ MCPFetcher& MCPFetcher::Walk(const FString& Path)
 		return *this;
 	}
 
-	// If no object yet, first segment is an asset path
-	int32 Start = 0;
+	for (int32 i = 0; i < Segments.Num(); i++)
+	{
 		if (!Obj && !ResultPin)
 		{
-		LoadUAsset(Segments[0]);
+			Asset(Segments[i]);
 			if (bError) return *this;
-		Start = 1;
+			continue;
 		}
 
-	const TArray<FWalker>& Walkers = GetWalkerTable();
-
-	// Walk each subsequent segment
-	for (int32 i = Start; i < Segments.Num(); i++)
-	{
 		FString Key, Value;
 		if (!Segments[i].Split(TEXT(":"), &Key, &Value))
 			Key = Segments[i];
 
-		bool bFound = false;
-		for (const FWalker& W : Walkers)
+		const FWalker* W = GetWalker(Key);
+		if (!W)
 		{
-			if (!StrEq(Key, W.Key)) continue;
-			(this->*W.Func)(Value);
-			bFound = true;
-			break;
-		}
-
-		if (!bFound)
-		{
-			SetError(FString::Printf(TEXT("Unknown walker '%s'"), *Key));
+			SetError(FString::Printf(TEXT("Unknown path step '%s'"), *Key));
 			return *this;
 		}
-
+		(this->*W->Func)(Value);
 		if (bError) return *this;
 	}
 
 	return *this;
 }
 
-void MCPFetcher::LoadUAsset(const FString& PackagePath)
+MCPFetcher& MCPFetcher::Asset(const FString& PackagePath)
 {
 	SetObj(LoadObject<UObject>(nullptr, *PackagePath));
 	if (!Obj)
@@ -105,6 +91,17 @@ void MCPFetcher::LoadUAsset(const FString& PackagePath)
 	// If this is a material open in the editor, use the editor's transient copy.
 	if (UMaterial* Mat = ::Cast<UMaterial>(Obj))
 		SetObj(MCPUtils::ReplaceMaterialWithTransientCopy(Mat));
+	return *this;
+}
+
+const MCPFetcher::FWalker* MCPFetcher::GetWalker(const FString& Key)
+{
+	for (const FWalker& W : GetWalkerTable())
+	{
+		if (StrEq(Key, W.Key))
+			return &W;
+	}
+	return nullptr;
 }
 
 MCPFetcher& MCPFetcher::Graph(const FString& Value)

Plugins/BlueprintMCP/Source/BlueprintMCP/Private/MCPUtils.cpp

@@ -72,6 +72,7 @@
 #include "MaterialGraph/MaterialGraphNode.h"
 #include "MaterialGraph/MaterialGraphSchema.h"
 #include "IMaterialEditor.h"
+#include "MaterialEditingLibrary.h"
 #include "Subsystems/AssetEditorSubsystem.h"
 
 // Mesh, animation, texture support
@@ -1125,6 +1126,8 @@ void MCPUtils::PreEdit(const TArray<UObject*>& Objects)
 
 void MCPUtils::PostEdit(const TArray<UObject*>& Objects)
 {
+	TSet<UMaterial*> Materials;
+	TSet<UBlueprint*> Blueprints;
 	for (int32 i = Objects.Num() - 1; i >= 0; --i)
 	{
 		UObject* Obj = Objects[i];
@@ -1132,8 +1135,36 @@ void MCPUtils::PostEdit(const TArray<UObject*>& Objects)
 		Obj->MarkPackageDirty();
 
 		if (UBlueprint* BP = Cast<UBlueprint>(Obj))
-			FBlueprintEditorUtils::MarkBlueprintAsStructurallyModified(BP);
+			Blueprints.Add(BP);
+
+		if (UMaterialInterface* MatIface = Cast<UMaterialInterface>(Obj))
+			if (UMaterial* BaseMat = MatIface->GetMaterial())
+				Materials.Add(BaseMat);
 	}
+	for (UMaterial *Material : Materials)
+		UMaterialEditingLibrary::RebuildMaterialInstanceEditors(Material);
+	for (UBlueprint *Blueprint : Blueprints)
+		FBlueprintEditorUtils::MarkBlueprintAsStructurallyModified(Blueprint);
+
+	if (GEditor)
+		GEditor->RedrawAllViewports();
+}
+
+TArray<MCPMaterialParameter> MCPUtils::MaterialParameters(UMaterialInstanceConstant *MI)
+{
+	TArray<MCPMaterialParameter> Results;
+	UMaterial* BaseMat = MI->GetMaterial();
+	if (!BaseMat) return Results;
+	for (UMaterialExpression* Expr : BaseMat->GetExpressions())
+	{
+		if (!Expr || !Expr->bIsParameterExpression) continue;
+		MCPMaterialParameter P;
+		P.Name = Expr->GetParameterName();
+		if (P.Name.IsNone()) continue;
+		if (!Expr->GetParameterValue(P.Metadata)) continue;
+		Results.Add(P);
+	}
+	return Results;
 }
 
 bool MCPUtils::SaveMaterialPackage(UMaterial* Material)
@@ -1790,6 +1821,19 @@ bool MCPUtils::SetPropertyValueText(UObject* Container, FProperty* Prop, const F
 	return true;
 }
 
+bool MCPUtils::SetPropertyValueText(void* Container, FProperty* Prop, const FString& Value, UObject* Owner, MCPErrorCallback Error)
+{
+	void* ValuePtr = Prop->ContainerPtrToValuePtr<void>(Container);
+	const TCHAR* ImportResult = Prop->ImportText_Direct(*Value, ValuePtr, Owner, PPF_None);
+	if (!ImportResult)
+	{
+		Error.SetError(FString::Printf(TEXT("Failed to parse '%s' for property '%s' (type: %s)"),
+			*Value, *FormatName(Prop), *Prop->GetCPPType()));
+		return false;
+	}
+	return true;
+}
+
 // ============================================================
 // SearchProperties
 // ============================================================

Plugins/BlueprintMCP/Source/BlueprintMCP/Public/MCPFetcher.h

@@ -35,6 +35,9 @@ public:
 	MCPFetcher(MCPErrorCallback CB) : ErrorCB(CB) {}
 	MCPFetcher(MCPErrorCallback CB, UObject* O) : Obj(O), ErrorCB(CB) {}
 
+	// Starting point is always Asset.
+	MCPFetcher& Asset(const FString& PackagePath);
+
 	// Walk one step.
 	MCPFetcher& Graph(const FString& Value);
 	MCPFetcher& Node(const FString& Value);
@@ -43,13 +46,13 @@ public:
 	MCPFetcher& LevelBlueprint(const FString& Value);
 	MCPFetcher& MatExp(const FString& Value);
 
+	// Parse string and walk multiple steps.
+	MCPFetcher& Walk(const FString& Path);
+
 	// C++-only walk step: resolve to the editable template
 	// (e.g. Blueprint → CDO, everything else → as-is).
 	MCPFetcher& Template();
 
-	// Parse string and walk multiple steps.
-	MCPFetcher& Walk(const FString& Path);
-
 	// Walker table entry.
 	struct FWalker
 	{
@@ -74,6 +77,7 @@ public:
 		return Result;
 	}
 
+
 private:
 	TArray<UObject*> Chain;
 	static bool StrEq(const FString& A, const TCHAR* B) { return A.Equals(B, ESearchCase::IgnoreCase); }
@@ -81,7 +85,7 @@ private:
 	void SetPin(UEdGraphPin* InPin) { ResultPin = InPin; Obj = nullptr; }
 	MCPFetcher& SetError(const FString& Msg);
 	MCPFetcher& TypeMismatch(const TCHAR* Walker, const TCHAR* Expected);
-	void LoadUAsset(const FString& PackagePath);
+	const FWalker* GetWalker(const FString& Key);
 };
 
 template<> inline UEdGraphPin* MCPFetcher::Cast<UEdGraphPin>()

Plugins/BlueprintMCP/Source/BlueprintMCP/Public/MCPUtils.h

@@ -3,6 +3,8 @@
 #include "CoreMinimal.h"
 #include "Dom/JsonObject.h"
 #include "EdGraph/EdGraphPin.h"
+#include "Materials/MaterialInstanceConstant.h"
+#include "MaterialTypes.h"
 
 class UBlueprint;
 class UEdGraph;
@@ -96,6 +98,12 @@ struct MCPErrorCallback
 	void SetError(const FString& Msg) const { Func(Msg); }
 };
 
+struct MCPMaterialParameter
+{
+	FName Name;
+	FMaterialParameterMetadata Metadata;
+};
+
 // Stateless utility functions used by MCP handlers and the MCP server.
 // This is effectively a namespace — all methods are static.
 class MCPUtils
@@ -277,6 +285,9 @@ public:
 	static void PreEdit(const TArray<UObject*>& Objects);
 	static void PostEdit(const TArray<UObject*>& Objects);
 
+	// ----- Material Instance -----
+	static TArray<MCPMaterialParameter> MaterialParameters(UMaterialInstanceConstant *MI);
+
 	// ----- Editable template -----
 	// Given an object, returns the appropriate template object for generic
 	// property editing, or nullptr if the type isn't whitelisted.
@@ -287,6 +298,7 @@ public:
 	static FProperty* FindPropertyByName(UObject* Obj, const FString& Name, MCPErrorCallback Error = nullptr);
 	static FString GetPropertyValueText(UObject* Container, FProperty* Prop);
 	static bool SetPropertyValueText(UObject* Container, FProperty* Prop, const FString& Value, MCPErrorCallback Error = nullptr);
+	static bool SetPropertyValueText(void* Container, FProperty* Prop, const FString& Value, UObject* Owner, MCPErrorCallback Error = nullptr);
 
 	// ----- Property population -----
 	static FString PropertyNameToJsonKey(const FString& PropName);