fix(truepbr): resolve MATO swap bug

src/TruePBR.cpp

@@ -1340,22 +1340,79 @@ struct TESBoundObject_Clone3D
 		auto* result = func(object, ref, arg3);
 		if (result != nullptr && ref != nullptr && ref->data.objectReference != nullptr && ref->data.objectReference->formType == RE::FormType::Static) {
 			auto* stat = static_cast<RE::TESObjectSTAT*>(ref->data.objectReference);
-			if (stat->data.materialObj != nullptr && stat->data.materialObj->directionalData.singlePass) {
-				if (auto* pbrData = truePBR->GetPBRMaterialObjectData(stat->data.materialObj)) {
-					RE::BSVisit::TraverseScenegraphGeometries(result, [pbrData](RE::BSGeometry* geometry) {
-						if (auto* shaderProperty = static_cast<RE::BSShaderProperty*>(geometry->GetGeometryRuntimeData().shaderProperty.get())) {
-							if (shaderProperty->GetMaterialType() == RE::BSShaderMaterial::Type::kLighting &&
-								shaderProperty->flags.any(RE::BSShaderProperty::EShaderPropertyFlag::kVertexLighting)) {
-								if (auto* material = static_cast<BSLightingShaderMaterialPBR*>(shaderProperty->material)) {
-									material->ApplyMaterialObjectData(*pbrData);
-									BSLightingShaderMaterialPBR::All[material].materialObjectData = pbrData;
+			RE::BGSMaterialObject* currentMato = stat->data.materialObj;
+
+			// Resolve PBR MATO data for the three-way condition as a single pointer:
+			//   non-null  -> apply MATO to geometries
+			//   null      -> clear any previously applied MATO from geometries
+			// This covers all negative cases (currentMato == nullptr, singlePass ==
+			// false, or no matching PBR entry) with one branch so the clear path is
+			// never silently skipped.
+			auto* pbrData = (currentMato != nullptr && currentMato->directionalData.singlePass) ? truePBR->GetPBRMaterialObjectData(currentMato) : nullptr;
+
+			if (pbrData != nullptr) {
+				RE::BSVisit::TraverseScenegraphGeometries(result, [pbrData, ref](RE::BSGeometry* geometry) {
+					if (auto* shaderProperty = static_cast<RE::BSShaderProperty*>(geometry->GetGeometryRuntimeData().shaderProperty.get())) {
+						if (shaderProperty->GetMaterialType() == RE::BSShaderMaterial::Type::kLighting &&
+							shaderProperty->flags.any(RE::BSShaderProperty::EShaderPropertyFlag::kVertexLighting)) {
+							if (auto* material = static_cast<BSLightingShaderMaterialPBR*>(shaderProperty->material)) {
+								auto& ext = BSLightingShaderMaterialPBR::All[material];
+								const auto prevOwnerRefID = ext.lastOwnerRefFormID;
+
+								// Fork-before-write: if this material instance is already owned
+								// by a different ref whose MATO payload differs from the incoming
+								// one, clone it so we don't contaminate the previous owner's
+								// geometry.  Use pointer identity: GetPBRMaterialObjectData
+								// returns stable addresses into pbrMaterialObjects, so two
+								// different MATOs always produce different pointers regardless of
+								// whether their individual fields (baseColorScale, roughness,
+								// specularLevel, glint) happen to match.
+								const bool wouldContaminate =
+									(prevOwnerRefID != 0) &&
+									(prevOwnerRefID != ref->GetFormID()) &&
+									(ext.materialObjectData != pbrData);
+
+								BSLightingShaderMaterialPBR* targetMat = material;
+
+								if (wouldContaminate) {
+									auto* freshMat = BSLightingShaderMaterialPBR::Make();
+									if (freshMat) {
+										freshMat->CopyMembers(material);
+										shaderProperty->material = freshMat;
+										targetMat = freshMat;
+									} else {
+										logger::warn("[TruePBR] failed to clone PBR material for ref {:08X}; skipping to avoid contamination", ref->GetFormID());
+										return RE::BSVisit::BSVisitControl::kContinue;
+									}
 								}
+
+								targetMat->ApplyMaterialObjectData(*pbrData);
+								auto& targetExt = BSLightingShaderMaterialPBR::All[targetMat];
+								targetExt.materialObjectData = pbrData;
+								targetExt.lastOwnerRefFormID = ref->GetFormID();
 							}
 						}
+					}
 
-						return RE::BSVisit::BSVisitControl::kContinue;
-					});
-				}
+					return RE::BSVisit::BSVisitControl::kContinue;
+				});
+			} else {
+				RE::BSVisit::TraverseScenegraphGeometries(result, [](RE::BSGeometry* geometry) {
+					if (auto* shaderProperty = static_cast<RE::BSShaderProperty*>(geometry->GetGeometryRuntimeData().shaderProperty.get())) {
+						if (shaderProperty->GetMaterialType() == RE::BSShaderMaterial::Type::kLighting &&
+							shaderProperty->flags.any(RE::BSShaderProperty::EShaderPropertyFlag::kVertexLighting)) {
+							if (auto* material = static_cast<BSLightingShaderMaterialPBR*>(shaderProperty->material)) {
+								auto& ext = BSLightingShaderMaterialPBR::All[material];
+								if (ext.materialObjectData != nullptr) {
+									material->ClearMaterialObjectData();
+									ext.materialObjectData = nullptr;
+									ext.lastOwnerRefFormID = 0;
+								}
+							}
+						}
+					}
+					return RE::BSVisit::BSVisitControl::kContinue;
+				});
 			}
 		}
 		return result;

src/TruePBR/BSLightingShaderMaterialPBR.cpp

@@ -151,6 +151,14 @@ void BSLightingShaderMaterialPBR::ApplyMaterialObjectData(const TruePBR::PBRMate
 	projectedMaterialGlintParameters = materialObjectData.glintParameters;
 }
 
+void BSLightingShaderMaterialPBR::ClearMaterialObjectData()
+{
+	projectedMaterialBaseColorScale = { 1.f, 1.f, 1.f };
+	projectedMaterialRoughness = 1.f;
+	projectedMaterialSpecularLevel = 0.04f;
+	projectedMaterialGlintParameters = GlintParameters{};
+}
+
 void BSLightingShaderMaterialPBR::OnLoadTextureSet(std::uint64_t arg1, RE::BSTextureSet* inTextureSet)
 {
 	const auto& stateData = globals::game::graphicsState->GetRuntimeData();

src/TruePBR/BSLightingShaderMaterialPBR.h

@@ -37,6 +37,10 @@ class BSLightingShaderMaterialPBR : public RE::BSLightingShaderMaterialBase
 	{
 		TruePBR::PBRTextureSetData* textureSetData = nullptr;
 		TruePBR::PBRMaterialObjectData* materialObjectData = nullptr;
+		/// FormID of the TESObjectREFR whose Clone3D call last wrote MATO data to this
+		/// material.  Used by the fork-before-write check to detect when a pooled material
+		/// instance would be overwritten by a different ref, triggering a clone instead.
+		RE::FormID lastOwnerRefFormID = 0;
 	};
 
 	inline static constexpr auto FEATURE = static_cast<RE::BSShaderMaterial::Feature>(32);
@@ -64,6 +68,10 @@ class BSLightingShaderMaterialPBR : public RE::BSLightingShaderMaterialBase
 
 	void ApplyTextureSetData(const TruePBR::PBRTextureSetData& textureSetData);
 	void ApplyMaterialObjectData(const TruePBR::PBRMaterialObjectData& materialObjectData);
+	/// Resets all projected-material fields to their default values.
+	/// Called on references that carry no MATO (or no PBR config for their MATO) to
+	/// prevent stale data copied in by CopyMembers from persisting on the material.
+	void ClearMaterialObjectData();
 
 	float GetRoughnessScale() const;
 	float GetSpecularLevel() const;