Changed the .material file format to use a flat list for material property values, instead of a tree structure.

This is needed to support deeply nested material property groups, it just makes the serialization code a lot simpler than trying to support nested groups in the .material file. It also makes the file more readable and easier to search all files for particular properties.
I also updated MaterialSourceData to hide the property values behind a clean API.

Signed-off-by: santorac <55155825+santorac@users.noreply.github.com>

Gems/Atom/Feature/Common/Code/Source/Material/MaterialConverterSystemComponent.cpp

@@ -82,9 +82,8 @@ namespace AZ
             // The source data for generating material asset
             sourceData.m_materialType = GetMaterialTypePath();
 
-            auto handleTexture = [&materialData, &sourceData](
-                                     const char* propertyTextureGroup, SceneAPI::DataTypes::IMaterialData::TextureMapType textureType) {
-                MaterialSourceData::PropertyMap& properties = sourceData.m_properties[propertyTextureGroup];
+            auto handleTexture = [&materialData, &sourceData](const char* propertyTextureGroup, SceneAPI::DataTypes::IMaterialData::TextureMapType textureType)
+            {
                 const AZStd::string& texturePath = materialData.GetTexture(textureType);
 
                 // Check to see if the image asset exists. If not, skip this texture map and just disable it.
@@ -101,7 +100,7 @@ namespace AZ
 
                 if (assetFound)
                 {
-                    properties["textureMap"] = texturePath;
+                    sourceData.SetPropertyValue(MaterialPropertyId{propertyTextureGroup, "textureMap"}, texturePath);
                 }
                 else if (!texturePath.empty())
                 {
@@ -120,7 +119,7 @@ namespace AZ
             {
                 anyPBRInUse = true;
                 handleTexture("baseColor", SceneAPI::DataTypes::IMaterialData::TextureMapType::BaseColor);
-                sourceData.m_properties["baseColor"]["textureBlendMode"] = AZStd::string("Lerp");
+                sourceData.SetPropertyValue(Name{"baseColor.textureBlendMode"}, AZStd::string("Lerp"));
             }
             else
             {
@@ -135,10 +134,10 @@ namespace AZ
             if (baseColor.has_value())
             {
                 anyPBRInUse = true;
-                sourceData.m_properties["baseColor"]["color"] = toColor(baseColor.value());
+                sourceData.SetPropertyValue(Name{"baseColor.color"}, toColor(baseColor.value()));
             }
 
-            sourceData.m_properties["opacity"]["factor"] = materialData.GetOpacity();
+            sourceData.SetPropertyValue(Name{"opacity.factor"}, materialData.GetOpacity());
 
             auto applyOptionalPropertiesFunc = [&sourceData, &anyPBRInUse](const auto& propertyGroup, const auto& propertyName, const auto& propertyOptional)
             {
@@ -147,7 +146,7 @@ namespace AZ
                 if (propertyOptional.has_value())
                 {
                     anyPBRInUse = true;
-                    sourceData.m_properties[propertyGroup][propertyName] = propertyOptional.value();
+                    sourceData.SetPropertyValue(MaterialPropertyId{propertyGroup, propertyName}, propertyOptional.value());
                 }
             };
 
@@ -160,7 +159,7 @@ namespace AZ
             applyOptionalPropertiesFunc("roughness", "useTexture", materialData.GetUseRoughnessMap());
 
             handleTexture("emissive", SceneAPI::DataTypes::IMaterialData::TextureMapType::Emissive);
-            sourceData.m_properties["emissive"]["color"] = toColor(materialData.GetEmissiveColor());
+            sourceData.SetPropertyValue(Name{"emissive.color"}, toColor(materialData.GetEmissiveColor()));
             applyOptionalPropertiesFunc("emissive", "intensity", materialData.GetEmissiveIntensity());
             applyOptionalPropertiesFunc("emissive", "useTexture", materialData.GetUseEmissiveMap());
 
@@ -171,7 +170,7 @@ namespace AZ
             {
                 // If it doesn't have the useColorMap property, then it's a non-PBR material and the baseColor
                 // texture needs to be set to the diffuse color.
-                sourceData.m_properties["baseColor"]["color"] = toColor(materialData.GetDiffuseColor());
+                sourceData.SetPropertyValue(Name{"baseColor.color"}, toColor(materialData.GetDiffuseColor()));
             }
             return true;
         }

Gems/Atom/RPI/Code/Include/Atom/RPI.Edit/Material/MaterialSourceData.h

@@ -59,17 +59,25 @@ namespace AZ
 
             uint32_t m_materialTypeVersion = 0; //!< The version of the material type that was used to configure this material
 
-            using PropertyMap = AZStd::map<AZStd::string, MaterialPropertyValue>;
-            using PropertyGroupMap = AZStd::map<AZStd::string, PropertyMap>;
-
-            PropertyGroupMap m_properties;
-
             enum class ApplyVersionUpdatesResult
             {
                 Failed,
                 NoUpdates,
                 UpdatesApplied
             };
+            
+            //! If the data was loaded from an old format file (i.e. where "properties" was a tree with property values nested under groups),
+            //! this converts to the new format where properties are stored in a flat list.
+            void ConvertToNewDataFormat();
+
+            // Note that even though we use an unordered map, the JSON serialization system is nice enough to sort the data when saving to JSON.
+            using PropertyValueMap = AZStd::unordered_map<Name, MaterialPropertyValue>;
+
+            void SetPropertyValue(const Name& propertyId, const MaterialPropertyValue& value);
+            const MaterialPropertyValue& GetPropertyValue(const Name& propertyId) const;
+            PropertyValueMap GetPropertyValues() const;
+            bool HasPropertyValue(const Name& propertyId) const;
+            void RemovePropertyValue(const Name& propertyId);
 
             //! Creates a MaterialAsset from the MaterialSourceData content.
             //! @param assetId ID for the MaterialAsset
@@ -96,8 +104,16 @@ namespace AZ
                 AZStd::unordered_set<AZStd::string>* sourceDependencies = nullptr) const;
 
         private:
+
             void ApplyPropertiesToAssetCreator(
                 AZ::RPI::MaterialAssetCreator& materialAssetCreator, const AZStd::string_view& materialSourceFilePath) const;
+
+            // @deprecated: Don't use "properties" in JSON, use "propertyValues" instead.
+            using PropertyGroupMap = AZStd::unordered_map<Name, PropertyValueMap>;
+            PropertyGroupMap m_propertiesOld;
+
+            PropertyValueMap m_propertyValues;
+            MaterialPropertyValue m_invalidValue;
         };
     } // namespace RPI
 } // namespace AZ

Gems/Atom/RPI/Code/Include/Atom/RPI.Edit/Material/MaterialTypeSourceData.h

@@ -216,11 +216,11 @@ namespace AZ
                 //! This field is unused, and has been replaced by MaterialTypeSourceData::m_version below. It is kept for legacy file compatibility to suppress warnings and errors.
                 uint32_t m_versionOld = 0;
 
-                //! [Deprecated] Use m_propertyGroups instead
+                //! @deprecated: Use m_propertyGroups instead
                 //! List of groups that will contain the available properties
                 AZStd::vector<GroupDefinition> m_groupsOld;
 
-                //! [Deprecated] Use m_propertyGroups instead
+                //! @deprecated: Use m_propertyGroups instead
                 AZStd::map<AZStd::string /*group name*/, AZStd::vector<PropertyDefinition>> m_propertiesOld;
                 
                 //! Collection of all available user-facing properties

Gems/Atom/RPI/Code/Include/Atom/RPI.Edit/Material/MaterialUtils.h

@@ -24,6 +24,7 @@ namespace AZ
 
     namespace RPI
     {
+        class MaterialSourceData;
         class MaterialTypeSourceData;
 
         namespace MaterialUtils
@@ -48,11 +49,14 @@ namespace AZ
             //! @return if resolving is successful. An error will be reported if it fails.
             bool ResolveMaterialPropertyEnumValue(const MaterialPropertyDescriptor* propertyDescriptor, const AZ::Name& enumName, MaterialPropertyValue& outResolvedValue);
 
-            //! Load material type from a json file. If the file path is relative, the loaded json document must be provided.
+            //! Load a material type from a json file. If the file path is relative, the loaded json document must be provided.
             //! Otherwise, it will use the passed in document first if not null, or load the json document from the path.
             //! @param filePath a relative path if document is provided, an absolute path if document is not provided.
             //! @param document the loaded json document.
             AZ::Outcome<MaterialTypeSourceData> LoadMaterialTypeSourceData(const AZStd::string& filePath, const rapidjson::Value* document = nullptr);
+            
+            //! Load a material from a json file.
+            AZ::Outcome<MaterialSourceData> LoadMaterialSourceData(const AZStd::string& filePath, const rapidjson::Value* document = nullptr, bool warningsAsErrors = false);
 
             //! Utility function for custom JSON serializers to report results as "Skipped" when encountering keys that aren't recognized
             //! as part of the custom format.

Gems/Atom/RPI/Code/Source/RPI.Builders/Material/MaterialBuilder.cpp

@@ -52,7 +52,7 @@ namespace AZ
         {
             AssetBuilderSDK::AssetBuilderDesc materialBuilderDescriptor;
             materialBuilderDescriptor.m_name = JobKey;
-            materialBuilderDescriptor.m_version = 117; // new material type file format
+            materialBuilderDescriptor.m_version = 119; // new material file format
             materialBuilderDescriptor.m_patterns.push_back(AssetBuilderSDK::AssetBuilderPattern("*.material", AssetBuilderSDK::AssetBuilderPattern::PatternType::Wildcard));
             materialBuilderDescriptor.m_patterns.push_back(AssetBuilderSDK::AssetBuilderPattern("*.materialtype", AssetBuilderSDK::AssetBuilderPattern::PatternType::Wildcard));
             materialBuilderDescriptor.m_busId = azrtti_typeid<MaterialBuilder>();
@@ -129,38 +129,6 @@ namespace AZ
             }
         }
 
-        template<typename MaterialSourceDataT>
-        AZ::Outcome<MaterialSourceDataT> LoadSourceData(const rapidjson::Value& value, const AZStd::string& filePath)
-        {
-            MaterialSourceDataT material;
-
-            JsonDeserializerSettings settings;
-
-            JsonReportingHelper reportingHelper;
-            reportingHelper.Attach(settings);
-
-            // This is required by some custom material serializers to support relative path references.
-            JsonFileLoadContext fileLoadContext;
-            fileLoadContext.PushFilePath(filePath);
-            settings.m_metadata.Add(fileLoadContext);
-
-            JsonSerialization::Load(material, value, settings);
-
-            if (reportingHelper.ErrorsReported())
-            {
-                return AZ::Failure();
-            }
-            else if (reportingHelper.WarningsReported())
-            {
-                AZ_Error(MaterialBuilderName, false, "Warnings reported while loading '%s'", filePath.c_str());
-                return AZ::Failure();
-            }
-            else
-            {
-                return AZ::Success(AZStd::move(material));
-            }
-        }
-
         void MaterialBuilder::CreateJobs(const AssetBuilderSDK::CreateJobsRequest& request, AssetBuilderSDK::CreateJobsResponse& response) const
         {
             if (m_isShuttingDown)
@@ -295,7 +263,7 @@ namespace AZ
         
         AZ::Data::Asset<MaterialAsset> MaterialBuilder::CreateMaterialAsset(AZStd::string_view materialSourceFilePath, const rapidjson::Value& json) const
         {
-            auto material = LoadSourceData<MaterialSourceData>(json, materialSourceFilePath);
+            auto material = MaterialUtils::LoadMaterialSourceData(materialSourceFilePath, &json, true);
 
             if (!material.IsSuccess())
             {

Gems/Atom/RPI/Code/Source/RPI.Edit/Material/MaterialSourceData.cpp

@@ -54,10 +54,11 @@ namespace AZ
                     ->Field("materialType", &MaterialSourceData::m_materialType)
                     ->Field("materialTypeVersion", &MaterialSourceData::m_materialTypeVersion)
                     ->Field("parentMaterial", &MaterialSourceData::m_parentMaterial)
-                    ->Field("properties", &MaterialSourceData::m_properties)
+                    ->Field("properties", &MaterialSourceData::m_propertiesOld)
+                    ->Field("propertyValues", &MaterialSourceData::m_propertyValues)
                     ;
 
-                serializeContext->RegisterGenericType<PropertyMap>();
+                serializeContext->RegisterGenericType<PropertyValueMap>();
                 serializeContext->RegisterGenericType<PropertyGroupMap>();
             }
         }
@@ -73,6 +74,55 @@ namespace AZ
             }
         }
         
+        void MaterialSourceData::SetPropertyValue(const Name& propertyId, const MaterialPropertyValue& value)
+        {
+            if (!propertyId.IsEmpty())
+            {
+                m_propertyValues[propertyId] = value;
+            }
+        }
+
+        const MaterialPropertyValue& MaterialSourceData::GetPropertyValue(const Name& propertyId) const
+        {
+            auto iter = m_propertyValues.find(propertyId);
+            if (iter == m_propertyValues.end())
+            {
+                return m_invalidValue;
+            }
+            else
+            {
+                return iter->second;
+            }
+        }
+        
+        void MaterialSourceData::RemovePropertyValue(const Name& propertyId)
+        {
+            m_propertyValues.erase(propertyId);
+        }
+        
+        MaterialSourceData::PropertyValueMap MaterialSourceData::GetPropertyValues() const
+        {
+            return m_propertyValues;
+        }
+
+        bool MaterialSourceData::HasPropertyValue(const Name& propertyId) const
+        {
+            return m_propertyValues.find(propertyId) != m_propertyValues.end();
+        }
+        
+        void MaterialSourceData::ConvertToNewDataFormat()
+        {
+            for (auto& [groupName, propertyList] : m_propertiesOld)
+            {
+                for (auto& [propertyName, propertyValue] : propertyList)
+                {
+                    SetPropertyValue(MaterialPropertyId{groupName, propertyName}, propertyValue);
+                }
+            }
+
+            m_propertiesOld.clear();
+        }
+
         Outcome<Data::Asset<MaterialAsset>> MaterialSourceData::CreateMaterialAsset(
             Data::AssetId assetId, AZStd::string_view materialSourceFilePath, MaterialAssetProcessingMode processingMode, bool elevateWarnings) const
         {
@@ -250,12 +300,14 @@ namespace AZ
                     return Failure();
                 }
 
-                MaterialSourceData parentSourceData;
-                if (!AZ::RPI::JsonUtils::LoadObjectFromFile(parentSourceAbsPath, parentSourceData))
+                auto loadParentResult = MaterialUtils::LoadMaterialSourceData(parentSourceAbsPath);
+                if (!loadParentResult)
                 {
                     AZ_Error("MaterialSourceData", false, "Failed to load MaterialSourceData for parent material: '%s'.", parentSourceAbsPath.c_str());
                     return Failure();
                 }
+                
+                MaterialSourceData parentSourceData = loadParentResult.TakeValue();
 
                 // Make sure that all materials in the hierarchy share the same material type
                 const auto parentTypeAssetId = AssetUtils::MakeAssetId(parentSourceAbsPath, parentSourceData.m_materialType, 0);
@@ -314,30 +366,29 @@ namespace AZ
         void MaterialSourceData::ApplyPropertiesToAssetCreator(
             AZ::RPI::MaterialAssetCreator& materialAssetCreator, const AZStd::string_view& materialSourceFilePath) const
         {
-            for (auto& group : m_properties)
+            for (auto& [propertyId, propertyValue] : m_propertyValues)
             {
-                for (auto& property : group.second)
+                if (!propertyValue.IsValid())
+                {
+                    materialAssetCreator.ReportWarning("Source data for material property value is invalid.");
+                }
+                else
                 {
-                    MaterialPropertyId propertyId{ group.first, property.first };
-                    if (!property.second.IsValid())
-                    {
-                        materialAssetCreator.ReportWarning("Source data for material property value is invalid.");
-                    }
                     // If the source value type is a string, there are two possible property types: Image and Enum. If there is a "." in
                     // the string (for the extension) we assume it's an Image and look up the referenced Asset. Otherwise, we can assume
                     // it's an Enum value and just preserve the original string.
-                    else if (property.second.Is<AZStd::string>() && AzFramework::StringFunc::Contains(property.second.GetValue<AZStd::string>(), "."))
+                    if (propertyValue.Is<AZStd::string>() && AzFramework::StringFunc::Contains(propertyValue.GetValue<AZStd::string>(), "."))
                     {
                         Data::Asset<ImageAsset> imageAsset;
 
                         MaterialUtils::GetImageAssetResult result = MaterialUtils::GetImageAssetReference(
-                            imageAsset, materialSourceFilePath, property.second.GetValue<AZStd::string>());
+                            imageAsset, materialSourceFilePath, propertyValue.GetValue<AZStd::string>());
                                     
                         if (result == MaterialUtils::GetImageAssetResult::Missing)
                         {
                             materialAssetCreator.ReportWarning(
                                 "Material property '%s': Could not find the image '%s'", propertyId.GetCStr(),
-                                property.second.GetValue<AZStd::string>().data());
+                                propertyValue.GetValue<AZStd::string>().data());
                         }
                                     
                         imageAsset.SetAutoLoadBehavior(Data::AssetLoadBehavior::PreLoad);
@@ -345,7 +396,7 @@ namespace AZ
                     }
                     else
                     {
-                        materialAssetCreator.SetPropertyValue(propertyId, property.second);
+                        materialAssetCreator.SetPropertyValue(propertyId, propertyValue);
                     }
                 }
             }

Gems/Atom/RPI/Code/Source/RPI.Edit/Material/MaterialTypeSourceData.cpp

@@ -100,9 +100,9 @@ namespace AZ
 
                 serializeContext->Class<PropertyLayout>()
                     ->Version(3) // Added propertyGroups
-                    ->Field("version", &PropertyLayout::m_versionOld)       //< Deprecated, preserved for backward compatibility, replaced by MaterialTypeSourceData::version
-                    ->Field("groups", &PropertyLayout::m_groupsOld)         //< Deprecated, preserved for backward compatibility, replaced by propertyGroups
-                    ->Field("properties", &PropertyLayout::m_propertiesOld) //< Deprecated, preserved for backward compatibility, replaced by propertyGroups
+                    ->Field("version", &PropertyLayout::m_versionOld)       //< @deprecated: preserved for backward compatibility, replaced by MaterialTypeSourceData::version
+                    ->Field("groups", &PropertyLayout::m_groupsOld)         //< @deprecated: preserved for backward compatibility, replaced by propertyGroups
+                    ->Field("properties", &PropertyLayout::m_propertiesOld) //< @deprecated: preserved for backward compatibility, replaced by propertyGroups
                     ->Field("propertyGroups", &PropertyLayout::m_propertyGroups)
                     ;
 

Gems/Atom/RPI/Code/Source/RPI.Edit/Material/MaterialUtils.cpp

@@ -12,6 +12,7 @@
 #include <Atom/RPI.Reflect/Image/StreamingImageAsset.h>
 #include <Atom/RPI.Reflect/Material/MaterialAsset.h>
 #include <Atom/RPI.Reflect/Material/MaterialTypeAsset.h>
+#include <Atom/RPI.Edit/Material/MaterialSourceData.h>
 #include <Atom/RPI.Edit/Material/MaterialTypeSourceData.h>
 #include <Atom/RPI.Edit/Common/JsonReportingHelper.h>
 #include <Atom/RPI.Edit/Common/JsonFileLoadContext.h>
@@ -82,7 +83,7 @@ namespace AZ
                     loadOutcome = AZ::JsonSerializationUtils::ReadJsonFile(filePath, AZ::RPI::JsonUtils::DefaultMaxFileSize);
                     if (!loadOutcome.IsSuccess())
                     {
-                        AZ_Error("AZ::RPI::JsonUtils", false, "%s", loadOutcome.GetError().c_str());
+                        AZ_Error("MaterialUtils", false, "%s", loadOutcome.GetError().c_str());
                         return AZ::Failure();
                     }
 
@@ -114,6 +115,46 @@ namespace AZ
                     return AZ::Success(AZStd::move(materialType));
                 }
             }
+            
+            AZ::Outcome<MaterialSourceData> LoadMaterialSourceData(const AZStd::string& filePath, const rapidjson::Value* document, bool warningsAsErrors)
+            {
+                AZ::Outcome<rapidjson::Document, AZStd::string> loadOutcome;
+                if (document == nullptr)
+                {
+                    loadOutcome = AZ::JsonSerializationUtils::ReadJsonFile(filePath, AZ::RPI::JsonUtils::DefaultMaxFileSize);
+                    if (!loadOutcome.IsSuccess())
+                    {
+                        AZ_Error("MaterialUtils", false, "%s", loadOutcome.GetError().c_str());
+                        return AZ::Failure();
+                    }
+
+                    document = &loadOutcome.GetValue();
+                }
+
+                MaterialSourceData material;
+
+                JsonDeserializerSettings settings;
+
+                JsonReportingHelper reportingHelper;
+                reportingHelper.Attach(settings);
+
+                JsonSerialization::Load(material, *document, settings);
+                material.ConvertToNewDataFormat();
+
+                if (reportingHelper.ErrorsReported())
+                {
+                    return AZ::Failure();
+                }
+                else if (warningsAsErrors && reportingHelper.WarningsReported())
+                {
+                    AZ_Error("MaterialUtils", false, "Warnings reported while loading '%s'", filePath.c_str());
+                    return AZ::Failure();
+                }
+                else
+                {
+                    return AZ::Success(AZStd::move(material));
+                }
+            }
 
             void CheckForUnrecognizedJsonFields(const AZStd::string_view* acceptedFieldNames, uint32_t acceptedFieldNameCount, const rapidjson::Value& object, JsonDeserializerContext& context, JsonSerializationResult::ResultCode &result)
             {

Gems/Atom/RPI/Code/Tests/Material/MaterialSourceDataTests.cpp

@@ -86,7 +86,7 @@ namespace UnitTest
 
             RPITestFixture::TearDown();
         }
-        
+
         Data::Asset<MaterialTypeAsset> CreateTestMaterialTypeAsset(Data::AssetId assetId)
         {
             const char* materialTypeJson = R"(
@@ -146,21 +146,21 @@ namespace UnitTest
                     }
                 )";
 
-
             MaterialTypeSourceData materialTypeSourceData;
             LoadTestDataFromJson(materialTypeSourceData, materialTypeJson);
             return materialTypeSourceData.CreateMaterialTypeAsset(assetId).TakeValue();
         }
     };
 
-    void AddPropertyGroup(MaterialSourceData& material, AZStd::string_view groupName)
+    void AddPropertyGroup(MaterialSourceData&, AZStd::string_view)
     {
-        material.m_properties.insert(groupName);
+        // Old function, left blank intentionally
     }
 
-    void AddProperty(MaterialSourceData& material, AZStd::string_view groupName, AZStd::string_view propertyName, const MaterialPropertyValue& anyValue)
+    void AddProperty(MaterialSourceData& material, AZStd::string_view groupName, AZStd::string_view propertyName, const MaterialPropertyValue& value)
     {
-        material.m_properties[groupName][propertyName] = anyValue;
+        MaterialPropertyId id{groupName, propertyName};
+        material.SetPropertyValue(id, value);
     }
 
     TEST_F(MaterialSourceDataTests, CreateMaterialAsset_BasicProperties)
@@ -359,80 +359,61 @@ namespace UnitTest
 
     void CheckEqual(MaterialSourceData& a, MaterialSourceData& b)
     {
-        EXPECT_STREQ(a.m_materialType.data(), b.m_materialType.data());
-        EXPECT_STREQ(a.m_description.data(), b.m_description.data());
-        EXPECT_STREQ(a.m_parentMaterial.data(), b.m_parentMaterial.data());
+        EXPECT_STREQ(a.m_materialType.c_str(), b.m_materialType.c_str());
+        EXPECT_STREQ(a.m_description.c_str(), b.m_description.c_str());
+        EXPECT_STREQ(a.m_parentMaterial.c_str(), b.m_parentMaterial.c_str());
         EXPECT_EQ(a.m_materialTypeVersion, b.m_materialTypeVersion);
 
-        EXPECT_EQ(a.m_properties.size(), b.m_properties.size());
-        for (auto& groupA : a.m_properties)
-        {
-            AZStd::string groupName = groupA.first;
+        EXPECT_EQ(a.GetPropertyValues().size(), b.GetPropertyValues().size());
 
-            auto groupIterB = b.m_properties.find(groupName);
-            if (groupIterB == b.m_properties.end())
+        for (auto& [propertyId, propertyValue] : a.GetPropertyValues())
+        {
+            if (!b.HasPropertyValue(propertyId))
             {
-                EXPECT_TRUE(false) << "groupB[" << groupName.c_str() << "] not found";
+                EXPECT_TRUE(false) << "Property '" << propertyId.GetCStr() << "' not found in material B";
                 continue;
             }
 
-            auto& groupB = *groupIterB;
-
-            EXPECT_EQ(groupA.second.size(), groupB.second.size()) << " for group[" << groupName.c_str() << "]";
-
-            for (auto& propertyIterA : groupA.second)
-            {
-                AZStd::string propertyName = propertyIterA.first;
+            auto& propertyA = propertyValue;
+            auto& propertyB = b.GetPropertyValue(propertyId);
 
-                auto propertyIterB = groupB.second.find(propertyName);
-                if (propertyIterB == groupB.second.end())
-                {
-                    EXPECT_TRUE(false) << "groupB[" << groupName.c_str() << "][" << propertyName.c_str() << "] not found";
-                    continue;
-                }
-
-                auto& propertyA = propertyIterA.second;
-                auto& propertyB = propertyIterB->second;
-
-                AZStd::string propertyReference = AZStd::string::format(" for property '%s.%s'", groupName.c_str(), propertyName.c_str());
+            AZStd::string propertyReference = AZStd::string::format(" for property '%s'", propertyId.GetCStr());
                 
-                // We allow some types like Vector4 and Color or Int and UInt to be interchangeable since they serialize the same and can be converted when the MaterialAsset is finalized.
+            // We allow some types like Vector4 and Color or Int and UInt to be interchangeable since they serialize the same and can be converted when the MaterialAsset is finalized.
 
-                if (AreTypesCompatible<bool>(propertyA, propertyB))
-                {
-                    EXPECT_EQ(propertyA.GetValue<bool>(), propertyB.GetValue<bool>()) << propertyReference.c_str();
-                }
-                else if (AreTypesCompatible<int32_t>(propertyA, propertyB))
-                {
-                    EXPECT_EQ(GetAsInt(propertyA), GetAsInt(propertyB)) << propertyReference.c_str();
-                }
-                else if (AreTypesCompatible<float>(propertyA, propertyB))
-                {
-                    EXPECT_NEAR(propertyA.GetValue<float>(),     propertyB.GetValue<float>(), 0.01) << propertyReference.c_str();
-                }
-                else if (AreTypesCompatible<Vector2>(propertyA, propertyB))
-                {
-                    EXPECT_TRUE(propertyA.GetValue<Vector2>().IsClose(propertyB.GetValue<Vector2>())) << propertyReference.c_str();
-                }
-                else if (AreTypesCompatible<Vector3>(propertyA, propertyB))
-                {
-                    EXPECT_TRUE(propertyA.GetValue<Vector3>().IsClose(propertyB.GetValue<Vector3>())) << propertyReference.c_str();
-                }
-                else if (AreTypesCompatible<Vector4>(propertyA, propertyB))
-                {
-                    EXPECT_TRUE(GetAsVector4(propertyA).IsClose(GetAsVector4(propertyB))) << propertyReference.c_str();
-                }
-                else if (AreTypesCompatible<AZStd::string>(propertyA, propertyB))
-                {
-                    EXPECT_STREQ(propertyA.GetValue<AZStd::string>().c_str(), propertyB.GetValue<AZStd::string>().c_str()) << propertyReference.c_str();
-                }
-                else
-                {
-                    ADD_FAILURE();
-                }
+            if (AreTypesCompatible<bool>(propertyA, propertyB))
+            {
+                EXPECT_EQ(propertyA.GetValue<bool>(), propertyB.GetValue<bool>()) << propertyReference.c_str();
+            }
+            else if (AreTypesCompatible<int32_t>(propertyA, propertyB))
+            {
+                EXPECT_EQ(GetAsInt(propertyA), GetAsInt(propertyB)) << propertyReference.c_str();
+            }
+            else if (AreTypesCompatible<float>(propertyA, propertyB))
+            {
+                EXPECT_NEAR(propertyA.GetValue<float>(),     propertyB.GetValue<float>(), 0.01) << propertyReference.c_str();
+            }
+            else if (AreTypesCompatible<Vector2>(propertyA, propertyB))
+            {
+                EXPECT_TRUE(propertyA.GetValue<Vector2>().IsClose(propertyB.GetValue<Vector2>())) << propertyReference.c_str();
+            }
+            else if (AreTypesCompatible<Vector3>(propertyA, propertyB))
+            {
+                EXPECT_TRUE(propertyA.GetValue<Vector3>().IsClose(propertyB.GetValue<Vector3>())) << propertyReference.c_str();
+            }
+            else if (AreTypesCompatible<Vector4>(propertyA, propertyB))
+            {
+                EXPECT_TRUE(GetAsVector4(propertyA).IsClose(GetAsVector4(propertyB))) << propertyReference.c_str();
+            }
+            else if (AreTypesCompatible<AZStd::string>(propertyA, propertyB))
+            {
+                EXPECT_STREQ(propertyA.GetValue<AZStd::string>().c_str(), propertyB.GetValue<AZStd::string>().c_str()) << propertyReference.c_str();
+            }
+            else
+            {
+                ADD_FAILURE();
             }
         }
-
     }
 
     TEST_F(MaterialSourceDataTests, TestJsonRoundTrip)
@@ -465,6 +446,88 @@ namespace UnitTest
 
         CheckEqual(sourceDataOriginal, sourceDataCopy);
     }
+    
+    TEST_F(MaterialSourceDataTests, TestLoadLegacyFormat)
+    {
+        const AZStd::string inputJson = R"(
+            {
+                "materialType": "test.materialtype", // Doesn't matter, this isn't loaded
+                "properties": {
+                    "groupA": {
+                        "myBool": true,
+                        "myInt": 5,
+                        "myFloat": 0.5
+                    },
+                    "groupB": {
+                        "myFloat2": [0.1, 0.2],
+                        "myFloat3": [0.3, 0.4, 0.5],
+                        "myFloat4": [0.6, 0.7, 0.8, 0.9],
+                        "myString": "Hello"
+                    }
+                }
+            }
+        )";
+
+        MaterialSourceData material;
+        LoadTestDataFromJson(material, inputJson);
+        material.ConvertToNewDataFormat();
+
+        MaterialSourceData expectedMaterial;
+        expectedMaterial.m_materialType = "test.materialtype";
+        expectedMaterial.SetPropertyValue(Name{"groupA.myBool"}, true);
+        expectedMaterial.SetPropertyValue(Name{"groupA.myInt"}, 5);
+        expectedMaterial.SetPropertyValue(Name{"groupA.myFloat"}, 0.5f);
+        expectedMaterial.SetPropertyValue(Name{"groupB.myFloat2"}, Vector2(0.1f, 0.2f));
+        expectedMaterial.SetPropertyValue(Name{"groupB.myFloat3"}, Vector3(0.3f, 0.4f, 0.5f));
+        expectedMaterial.SetPropertyValue(Name{"groupB.myFloat4"}, Vector4(0.6f, 0.7f, 0.8f, 0.9f));
+        expectedMaterial.SetPropertyValue(Name{"groupB.myString"}, AZStd::string{"Hello"});
+
+        CheckEqual(expectedMaterial, material);
+    }
+    
+    TEST_F(MaterialSourceDataTests, TestPropertyValues)
+    {
+        MaterialSourceData material;
+        
+        Name foo{"foo"};
+        Name bar{"bar"};
+        Name baz{"baz"};
+
+        EXPECT_EQ(0, material.GetPropertyValues().size());
+        EXPECT_FALSE(material.HasPropertyValue(foo));
+        EXPECT_FALSE(material.HasPropertyValue(bar));
+        EXPECT_FALSE(material.HasPropertyValue(baz));
+        EXPECT_FALSE(material.GetPropertyValue(foo).IsValid());
+        EXPECT_FALSE(material.GetPropertyValue(bar).IsValid());
+        EXPECT_FALSE(material.GetPropertyValue(baz).IsValid());
+
+        material.SetPropertyValue(Name{"foo"}, 2);
+        material.SetPropertyValue(Name{"bar"}, true);
+        material.SetPropertyValue(Name{"baz"}, 0.5f);
+        
+        EXPECT_EQ(3, material.GetPropertyValues().size());
+        EXPECT_TRUE(material.HasPropertyValue(foo));
+        EXPECT_TRUE(material.HasPropertyValue(bar));
+        EXPECT_TRUE(material.HasPropertyValue(baz));
+        EXPECT_TRUE(material.GetPropertyValue(foo).IsValid());
+        EXPECT_TRUE(material.GetPropertyValue(bar).IsValid());
+        EXPECT_TRUE(material.GetPropertyValue(baz).IsValid());
+        EXPECT_EQ(material.GetPropertyValue(foo).GetValue<int32_t>(), 2);
+        EXPECT_EQ(material.GetPropertyValue(bar).GetValue<bool>(), true);
+        EXPECT_EQ(material.GetPropertyValue(baz).GetValue<float>(), 0.5f);
+
+        material.RemovePropertyValue(bar);
+        
+        EXPECT_EQ(2, material.GetPropertyValues().size());
+        EXPECT_TRUE(material.HasPropertyValue(foo));
+        EXPECT_FALSE(material.HasPropertyValue(bar));
+        EXPECT_TRUE(material.HasPropertyValue(baz));
+        EXPECT_TRUE(material.GetPropertyValue(foo).IsValid());
+        EXPECT_FALSE(material.GetPropertyValue(bar).IsValid());
+        EXPECT_TRUE(material.GetPropertyValue(baz).IsValid());
+        EXPECT_EQ(material.GetPropertyValue(foo).GetValue<int32_t>(), 2);
+        EXPECT_EQ(material.GetPropertyValue(baz).GetValue<float>(), 0.5f);
+    }
 
     TEST_F(MaterialSourceDataTests, Load_MaterialTypeAfterPropertyList)
     {
@@ -487,21 +550,14 @@ namespace UnitTest
             }
         )";
 
-        const char* materialTypeFilePath = "@exefolder@/Temp/simpleMaterialType.materialtype";
-
-        AZ::IO::FileIOStream file;
-        EXPECT_TRUE(file.Open(materialTypeFilePath, AZ::IO::OpenMode::ModeWrite | AZ::IO::OpenMode::ModeCreatePath));
-        file.Write(simpleMaterialTypeJson.size(), simpleMaterialTypeJson.data());
-        file.Close();
+        AZ::Utils::WriteFile(simpleMaterialTypeJson, "@exefolder@/Temp/simpleMaterialType.materialtype");
 
         // It shouldn't matter whether the materialType field appears before the property value list. This allows for the possibility
         // that customer scripts generate material data and happen to use an unexpected order.
         const AZStd::string inputJson = R"(
         {
-            "properties": {
-                "general": {
-                    "testValue": 1.2
-                }
+            "propertyValues": {
+                "general.testValue": 1.2
             },
             "materialType": "@exefolder@/Temp/simpleMaterialType.materialtype"
         }
@@ -513,7 +569,7 @@ namespace UnitTest
         EXPECT_EQ(AZ::JsonSerializationResult::Tasks::ReadField, loadResult.m_jsonResultCode.GetTask());
         EXPECT_EQ(AZ::JsonSerializationResult::Processing::Completed, loadResult.m_jsonResultCode.GetProcessing());
 
-        float testValue = material.m_properties["general"]["testValue"].GetValue<float>();
+        float testValue = material.GetPropertyValue(Name{"general.testValue"}).GetValue<float>();
         EXPECT_FLOAT_EQ(1.2f, testValue);
     }
     
@@ -522,10 +578,8 @@ namespace UnitTest
         const AZStd::string inputJson = R"(
             {
                 "materialTypeVersion": 1,
-                "properties": {
-                    "baseColor": {
-                        "color": [1.0,1.0,1.0]
-                    }
+                "propertyValues": {
+                    "baseColor.color": [1.0,1.0,1.0]
                 }
             }
         )";
@@ -561,10 +615,8 @@ namespace UnitTest
             {
                 "materialType": "DoesNotExist.materialtype",
                 "materialTypeVersion": 1,
-                "properties": {
-                    "baseColor": {
-                        "color": [1.0,1.0,1.0]
-                    }
+                "propertyValues": {
+                    "baseColor.color": [1.0,1.0,1.0]
                 }
             }
         )";
@@ -900,10 +952,8 @@ namespace UnitTest
         const AZStd::string inputJson = AZStd::string::format(R"(
             {
                 "materialType": "@exefolder@/Temp/test.materialtype",
-                "properties": {
-                    "%s": {
-                        "%s": %s
-                    }
+                "propertyValues": {
+                    "%s.%s": %s
                 }
             }
         )", groupName, propertyName, jsonValue);
@@ -965,7 +1015,239 @@ namespace UnitTest
         CheckEndToEndDataTypeResolution("MyFloat4", "{\"y\":0.2, \"x\":0.1, \"Z\":0.3}", Vector4{0.1f, 0.2f, 0.3f, 0.0f});
         CheckEndToEndDataTypeResolution("MyFloat4", "{\"y\":0.2, \"W\":0.4, \"x\":0.1, \"Z\":0.3}", Vector4{0.1f, 0.2f, 0.3f, 0.4f});
     }
+
+    TEST_F(MaterialSourceDataTests, CreateMaterialAssetFromSourceData_MultiLevelDataInheritance)
+    {
+        // Note the data being tested here is based on CreateMaterialAsset_MultiLevelDataInheritance()
+
+        const AZStd::string simpleMaterialTypeJson = R"(
+            {
+                "propertyLayout": {
+                    "propertyGroups":
+                    [
+                        {
+                            "name": "general",
+                            "properties": [
+                                {
+                                    "name": "MyFloat",
+                                    "type": "Float"
+                                },
+                                {
+                                    "name": "MyFloat2",
+                                    "type": "Vector2"
+                                },
+                                {
+                                    "name": "MyColor",
+                                    "type": "Color"
+                                }
+                            ]
+                        }
+                    ]
+                }
+            }
+        )";
+
+        AZ::Utils::WriteFile(simpleMaterialTypeJson, "@exefolder@/Temp/test.materialtype");
+
+        const AZStd::string material1Json = R"(
+            {
+                "materialType": "@exefolder@/Temp/test.materialtype",
+                "propertyValues": {
+                    "general.MyFloat": 1.5,
+                    "general.MyColor": [0.1, 0.2, 0.3, 0.4]
+                }
+            }
+        )";
+        
+        AZ::Utils::WriteFile(material1Json, "@exefolder@/Temp/m1.material");
+        
+        const AZStd::string material2Json = R"(
+            {
+                "materialType": "@exefolder@/Temp/test.materialtype",
+                "parentMaterial": "@exefolder@/Temp/m1.material",
+                "propertyValues": {
+                    "general.MyFloat2": [4.1, 4.2],
+                    "general.MyColor": [0.15, 0.25, 0.35, 0.45]
+                }
+            }
+        )";
+        
+        AZ::Utils::WriteFile(material2Json, "@exefolder@/Temp/m2.material");
+        
+        const AZStd::string material3Json = R"(
+            {
+                "materialType": "@exefolder@/Temp/test.materialtype",
+                "parentMaterial": "@exefolder@/Temp/m2.material",
+                "propertyValues": {
+                    "general.MyFloat": 3.5
+                }
+            }
+        )";
+        
+        AZ::Utils::WriteFile(material3Json, "@exefolder@/Temp/m3.material");
+        
+        MaterialSourceData sourceDataLevel1 = MaterialUtils::LoadMaterialSourceData("@exefolder@/Temp/m1.material").TakeValue();
+        MaterialSourceData sourceDataLevel2 = MaterialUtils::LoadMaterialSourceData("@exefolder@/Temp/m2.material").TakeValue();
+        MaterialSourceData sourceDataLevel3 = MaterialUtils::LoadMaterialSourceData("@exefolder@/Temp/m3.material").TakeValue();
+        
+        auto materialAssetLevel1 = sourceDataLevel1.CreateMaterialAssetFromSourceData(Uuid::CreateRandom());
+        EXPECT_TRUE(materialAssetLevel1.IsSuccess());
+        EXPECT_TRUE(materialAssetLevel1.GetValue()->WasPreFinalized());
+
+        auto materialAssetLevel2 = sourceDataLevel2.CreateMaterialAssetFromSourceData(Uuid::CreateRandom());
+        EXPECT_TRUE(materialAssetLevel2.IsSuccess());
+        EXPECT_TRUE(materialAssetLevel2.GetValue()->WasPreFinalized());
+
+        auto materialAssetLevel3 = sourceDataLevel3.CreateMaterialAssetFromSourceData(Uuid::CreateRandom());
+        EXPECT_TRUE(materialAssetLevel3.IsSuccess());
+        EXPECT_TRUE(materialAssetLevel3.GetValue()->WasPreFinalized());
+
+        auto layout = materialAssetLevel1.GetValue()->GetMaterialPropertiesLayout();
+        MaterialPropertyIndex myFloat = layout->FindPropertyIndex(Name("general.MyFloat"));
+        MaterialPropertyIndex myFloat2 = layout->FindPropertyIndex(Name("general.MyFloat2"));
+        MaterialPropertyIndex myColor = layout->FindPropertyIndex(Name("general.MyColor"));
+
+        AZStd::span<const MaterialPropertyValue> properties;
+
+        // Check level 1 properties
+        properties = materialAssetLevel1.GetValue()->GetPropertyValues();
+        EXPECT_EQ(properties[myFloat.GetIndex()].GetValue<float>(), 1.5f);
+        EXPECT_EQ(properties[myFloat2.GetIndex()].GetValue<Vector2>(), Vector2(0.0f, 0.0f));
+        EXPECT_EQ(properties[myColor.GetIndex()].GetValue<Color>(), Color(0.1f, 0.2f, 0.3f, 0.4f));
+
+        // Check level 2 properties
+        properties = materialAssetLevel2.GetValue()->GetPropertyValues();
+        EXPECT_EQ(properties[myFloat.GetIndex()].GetValue<float>(), 1.5f);
+        EXPECT_EQ(properties[myFloat2.GetIndex()].GetValue<Vector2>(), Vector2(4.1f, 4.2f));
+        EXPECT_EQ(properties[myColor.GetIndex()].GetValue<Color>(), Color(0.15f, 0.25f, 0.35f, 0.45f));
+
+        // Check level 3 properties
+        properties = materialAssetLevel3.GetValue()->GetPropertyValues();
+        EXPECT_EQ(properties[myFloat.GetIndex()].GetValue<float>(), 3.5f);
+        EXPECT_EQ(properties[myFloat2.GetIndex()].GetValue<Vector2>(), Vector2(4.1f, 4.2f));
+        EXPECT_EQ(properties[myColor.GetIndex()].GetValue<Color>(), Color(0.15f, 0.25f, 0.35f, 0.45f));
+    }
     
+    TEST_F(MaterialSourceDataTests, CreateMaterialAssetFromSourceData_MultiLevelDataInheritance_OldFormat)
+    {
+        // This test is the same as CreateMaterialAssetFromSourceData_MultiLevelDataInheritance except it uses the old format
+        // where material property values in the .material file were nested, with properties listed under a group object,
+        // rather than using a flat list of property values.
+        // Basically, we are making sure that MaterialSourceData::ConvertToNewDataFormat() is getting called.
+
+        const AZStd::string simpleMaterialTypeJson = R"(
+            {
+                "propertyLayout": {
+                    "propertyGroups":
+                    [
+                        {
+                            "name": "general",
+                            "properties": [
+                                {
+                                    "name": "MyFloat",
+                                    "type": "Float"
+                                },
+                                {
+                                    "name": "MyFloat2",
+                                    "type": "Vector2"
+                                },
+                                {
+                                    "name": "MyColor",
+                                    "type": "Color"
+                                }
+                            ]
+                        }
+                    ]
+                }
+            }
+        )";
+
+        AZ::Utils::WriteFile(simpleMaterialTypeJson, "@exefolder@/Temp/test.materialtype");
+
+        const AZStd::string material1Json = R"(
+            {
+                "materialType": "@exefolder@/Temp/test.materialtype",
+                "properties": {
+                    "general": {
+                        "MyFloat": 1.5,
+                        "MyColor": [0.1, 0.2, 0.3, 0.4]
+                    }
+                }
+            }
+        )";
+        
+        AZ::Utils::WriteFile(material1Json, "@exefolder@/Temp/m1.material");
+        
+        const AZStd::string material2Json = R"(
+            {
+                "materialType": "@exefolder@/Temp/test.materialtype",
+                "parentMaterial": "@exefolder@/Temp/m1.material",
+                "properties": {
+                    "general": {
+                        "MyFloat2": [4.1, 4.2],
+                        "MyColor": [0.15, 0.25, 0.35, 0.45]
+                    }
+                }
+            }
+        )";
+        
+        AZ::Utils::WriteFile(material2Json, "@exefolder@/Temp/m2.material");
+        
+        const AZStd::string material3Json = R"(
+            {
+                "materialType": "@exefolder@/Temp/test.materialtype",
+                "parentMaterial": "@exefolder@/Temp/m2.material",
+                "properties": {
+                    "general": {
+                        "MyFloat": 3.5
+                    }
+                }
+            }
+        )";
+        
+        AZ::Utils::WriteFile(material3Json, "@exefolder@/Temp/m3.material");
+        
+        MaterialSourceData sourceDataLevel1 = MaterialUtils::LoadMaterialSourceData("@exefolder@/Temp/m1.material").TakeValue();
+        MaterialSourceData sourceDataLevel2 = MaterialUtils::LoadMaterialSourceData("@exefolder@/Temp/m2.material").TakeValue();
+        MaterialSourceData sourceDataLevel3 = MaterialUtils::LoadMaterialSourceData("@exefolder@/Temp/m3.material").TakeValue();
+        
+        auto materialAssetLevel1 = sourceDataLevel1.CreateMaterialAssetFromSourceData(Uuid::CreateRandom());
+        EXPECT_TRUE(materialAssetLevel1.IsSuccess());
+        EXPECT_TRUE(materialAssetLevel1.GetValue()->WasPreFinalized());
+
+        auto materialAssetLevel2 = sourceDataLevel2.CreateMaterialAssetFromSourceData(Uuid::CreateRandom());
+        EXPECT_TRUE(materialAssetLevel2.IsSuccess());
+        EXPECT_TRUE(materialAssetLevel2.GetValue()->WasPreFinalized());
+
+        auto materialAssetLevel3 = sourceDataLevel3.CreateMaterialAssetFromSourceData(Uuid::CreateRandom());
+        EXPECT_TRUE(materialAssetLevel3.IsSuccess());
+        EXPECT_TRUE(materialAssetLevel3.GetValue()->WasPreFinalized());
+
+        auto layout = materialAssetLevel1.GetValue()->GetMaterialPropertiesLayout();
+        MaterialPropertyIndex myFloat = layout->FindPropertyIndex(Name("general.MyFloat"));
+        MaterialPropertyIndex myFloat2 = layout->FindPropertyIndex(Name("general.MyFloat2"));
+        MaterialPropertyIndex myColor = layout->FindPropertyIndex(Name("general.MyColor"));
+
+        AZStd::span<const MaterialPropertyValue> properties;
+
+        // Check level 1 properties
+        properties = materialAssetLevel1.GetValue()->GetPropertyValues();
+        EXPECT_EQ(properties[myFloat.GetIndex()].GetValue<float>(), 1.5f);
+        EXPECT_EQ(properties[myFloat2.GetIndex()].GetValue<Vector2>(), Vector2(0.0f, 0.0f));
+        EXPECT_EQ(properties[myColor.GetIndex()].GetValue<Color>(), Color(0.1f, 0.2f, 0.3f, 0.4f));
+
+        // Check level 2 properties
+        properties = materialAssetLevel2.GetValue()->GetPropertyValues();
+        EXPECT_EQ(properties[myFloat.GetIndex()].GetValue<float>(), 1.5f);
+        EXPECT_EQ(properties[myFloat2.GetIndex()].GetValue<Vector2>(), Vector2(4.1f, 4.2f));
+        EXPECT_EQ(properties[myColor.GetIndex()].GetValue<Color>(), Color(0.15f, 0.25f, 0.35f, 0.45f));
+
+        // Check level 3 properties
+        properties = materialAssetLevel3.GetValue()->GetPropertyValues();
+        EXPECT_EQ(properties[myFloat.GetIndex()].GetValue<float>(), 3.5f);
+        EXPECT_EQ(properties[myFloat2.GetIndex()].GetValue<Vector2>(), Vector2(4.1f, 4.2f));
+        EXPECT_EQ(properties[myColor.GetIndex()].GetValue<Color>(), Color(0.15f, 0.25f, 0.35f, 0.45f));
+    }
 }
 
 

Gems/Atom/Tools/MaterialEditor/Code/Source/Document/MaterialDocument.cpp

@@ -362,8 +362,8 @@ namespace MaterialEditor
                     }
                     
                     // TODO: Support populating the Material Editor with nested property groups, not just the top level.
-                    const AZStd::string groupName = propertyId.GetStringView().substr(0, propertyId.GetStringView().size() - propertyDefinition->GetName().size() - 1);
-                    sourceData.m_properties[groupName][propertyDefinition->GetName()] = propertyValue;
+                    AZStd::string_view groupName = propertyId.GetStringView().substr(0, propertyId.GetStringView().size() - propertyDefinition->GetName().size() - 1);
+                    sourceData.SetPropertyValue(AZ::RPI::MaterialPropertyId{groupName, propertyDefinition->GetName()}, propertyValue);
                 }
             }
             return true;
@@ -395,12 +395,15 @@ namespace MaterialEditor
         if (AzFramework::StringFunc::Path::IsExtension(m_absolutePath.c_str(), AZ::RPI::MaterialSourceData::Extension))
         {
             // Load the material source data so that we can check properties and create a material asset from it
-            if (!AZ::RPI::JsonUtils::LoadObjectFromFile(m_absolutePath, m_materialSourceData))
+            auto loadResult = AZ::RPI::MaterialUtils::LoadMaterialSourceData(m_absolutePath);
+            if (!loadResult)
             {
                 AZ_Error("MaterialDocument", false, "Material source data could not be loaded: '%s'.", m_absolutePath.c_str());
                 return OpenFailed();
             }
 
+            m_materialSourceData = loadResult.TakeValue();
+
             // We always need the absolute path for the material type and parent material to load source data and resolving
             // relative paths when saving. This will convert and store them as absolute paths for use within the document.
             if (!m_materialSourceData.m_parentMaterial.empty())
@@ -482,12 +485,15 @@ namespace MaterialEditor
         if (!m_materialSourceData.m_parentMaterial.empty())
         {
             AZ::RPI::MaterialSourceData parentMaterialSourceData;
-            if (!AZ::RPI::JsonUtils::LoadObjectFromFile(m_materialSourceData.m_parentMaterial, parentMaterialSourceData))
+            auto loadResult = AZ::RPI::MaterialUtils::LoadMaterialSourceData(m_materialSourceData.m_parentMaterial);
+            if (!loadResult)
             {
                 AZ_Error("MaterialDocument", false, "Material parent source data could not be loaded for: '%s'.", m_materialSourceData.m_parentMaterial.c_str());
                 return OpenFailed();
             }
 
+            parentMaterialSourceData = loadResult.TakeValue();
+
             const auto parentMaterialAssetIdResult = AZ::RPI::AssetUtils::MakeAssetId(m_materialSourceData.m_parentMaterial, 0);
             if (!parentMaterialAssetIdResult)
             {

Gems/AtomLyIntegration/CommonFeatures/Code/Source/Material/EditorMaterialComponentUtil.cpp

@@ -149,8 +149,8 @@ namespace AZ
                         }
 
                         // TODO: Support populating the Material Editor with nested property groups, not just the top level.
-                        const AZStd::string groupName = propertyId.GetStringView().substr(0, propertyId.GetStringView().size() - propertyDefinition->GetName().size() - 1);
-                        exportData.m_properties[groupName][propertyDefinition->GetName()] = propertyValue;
+                        AZStd::string_view groupName = propertyId.GetStringView().substr(0, propertyId.GetStringView().size() - propertyDefinition->GetName().size() - 1);
+                        exportData.SetPropertyValue(RPI::MaterialPropertyId{groupName, propertyDefinition->GetName()}, propertyValue);
                         return true;
                     });