Merge branch 'main' into hultonha_LYN-2315_camera-phase-2

Code/Framework/AzCore/AzCore/AzCoreModule.cpp

@@ -19,7 +19,6 @@
 #include <AzCore/Jobs/JobManagerComponent.h>
 #include <AzCore/Serialization/Json/JsonSystemComponent.h>
 #include <AzCore/Memory/MemoryComponent.h>
-#include <AzCore/NativeUI/NativeUISystemComponent.h>
 #include <AzCore/Script/ScriptSystemComponent.h>
 #include <AzCore/Slice/SliceComponent.h>
 #include <AzCore/Slice/SliceSystemComponent.h>
@@ -43,7 +42,6 @@ namespace AZ
             AssetManagerComponent::CreateDescriptor(),
             UserSettingsComponent::CreateDescriptor(),
             Debug::FrameProfilerComponent::CreateDescriptor(),
-            NativeUI::NativeUISystemComponent::CreateDescriptor(),
             SliceComponent::CreateDescriptor(),
             SliceSystemComponent::CreateDescriptor(),
             SliceMetadataInfoComponent::CreateDescriptor(),

Code/Framework/AzCore/AzCore/Component/ComponentApplication.cpp

@@ -28,6 +28,8 @@
 #include <AzCore/Memory/AllocatorManager.h>
 #include <AzCore/Memory/MallocSchema.h>
 
+#include <AzCore/NativeUI/NativeUIRequests.h>
+
 #include <AzCore/Serialization/EditContext.h>
 #include <AzCore/Serialization/ObjectStream.h>
 #include <AzCore/Serialization/Utils.h>
@@ -424,7 +426,7 @@ namespace AZ
 
         // Now that the Allocators are initialized, the Command Line parameters can be parsed
         m_commandLine.Parse(m_argC, m_argV);
-        ParseCommandLine(m_commandLine);
+        SettingsRegistryMergeUtils::ParseCommandLine(m_commandLine);
 
         // Create the settings registry and register it with the AZ interface system
         // This is done after the AppRoot has been calculated so that the Bootstrap.cfg
@@ -527,10 +529,42 @@ namespace AZ
         DestroyAllocator();
     }
 
+
+    void ReportBadEngineRoot()
+    {
+        AZStd::string errorMessage = {"Unable to determine a valid path to the engine.\n"
+                                      "Check parameters such as --project-path and --engine-path and make sure they are valid.\n"};
+        if (auto registry = AZ::SettingsRegistry::Get(); registry != nullptr)
+        {
+            AZ::SettingsRegistryInterface::FixedValueString filePathErrorStr;
+            if (registry->Get(filePathErrorStr, AZ::SettingsRegistryMergeUtils::FilePathKey_ErrorText); !filePathErrorStr.empty())
+            {
+                errorMessage += "Additional Info:\n";
+                errorMessage += filePathErrorStr.c_str();
+            }
+        }
+
+        if (auto nativeUI = AZ::Interface<AZ::NativeUI::NativeUIRequests>::Get(); nativeUI != nullptr)
+        {
+            nativeUI->DisplayOkDialog("O3DE Fatal Error", errorMessage.c_str(), false);
+        }
+        else
+        {
+            AZ_Error("ComponentApplication", false, "O3DE Fatal Error: %s\n", errorMessage.c_str());
+        }
+    }
+
+
     Entity* ComponentApplication::Create(const Descriptor& descriptor, const StartupParameters& startupParameters)
     {
         AZ_Assert(!m_isStarted, "Component application already started!");
 
+        if (m_engineRoot.empty())
+        {
+            ReportBadEngineRoot();
+            return nullptr;
+        }
+
         m_startupParameters = startupParameters;
 
         m_descriptor = descriptor;
@@ -871,46 +905,6 @@ namespace AZ
         }
     }
 
-    void ComponentApplication::ParseCommandLine(const AZ::CommandLine& commandLine)
-    {
-        struct OptionKeyToRegsetKey
-        {
-            AZStd::string_view m_optionKey;
-            AZStd::string m_regsetKey;
-        };
-
-        // Provide overrides for the engine root, the project root and the project cache root
-        AZStd::array commandOptions = {
-            OptionKeyToRegsetKey{ "engine-path", AZStd::string::format("%s/engine_path", AZ::SettingsRegistryMergeUtils::BootstrapSettingsRootKey) },
-            OptionKeyToRegsetKey{ "project-path", AZStd::string::format("%s/project_path", AZ::SettingsRegistryMergeUtils::BootstrapSettingsRootKey) },
-            OptionKeyToRegsetKey{ "project-cache-path", AZStd::string::format("%s/project_cache_path", AZ::SettingsRegistryMergeUtils::BootstrapSettingsRootKey) }
-        };
-
-        AZStd::fixed_vector<AZStd::string, commandOptions.size()> overrideArgs;
-
-        for (auto&& [optionKey, regsetKey] : commandOptions)
-        {
-            if (size_t optionCount = commandLine.GetNumSwitchValues(optionKey); optionCount > 0)
-            {
-                // Use the last supplied command option value to override previous values
-                auto overrideArg = AZStd::string::format(R"(--regset="%s=%s")", regsetKey.c_str(),
-                    commandLine.GetSwitchValue(optionKey, optionCount - 1).c_str());
-                overrideArgs.emplace_back(AZStd::move(overrideArg));
-            }
-        }
-
-        if (!overrideArgs.empty())
-        {
-            // Dump the input command line, add the additional option overrides
-            // and Parse the new command line into the Component Application command line
-            AZ::CommandLine::ParamContainer commandLineArgs;
-            commandLine.Dump(commandLineArgs);
-            commandLineArgs.insert(commandLineArgs.end(), AZStd::make_move_iterator(overrideArgs.begin()),
-                AZStd::make_move_iterator(overrideArgs.end()));
-            m_commandLine.Parse(commandLineArgs);
-        }
-    }
-
     void ComponentApplication::MergeSettingsToRegistry(SettingsRegistryInterface& registry)
     {
         SettingsRegistryInterface::Specializations specializations;

Code/Framework/AzCore/AzCore/Component/ComponentApplication.h

@@ -328,9 +328,6 @@ namespace AZ
         /// Create the drillers
         void        CreateDrillers();
 
-        /// Parse ComponentApplication specific command line arguments
-        void ParseCommandLine(const AZ::CommandLine& commandLine);
-
         virtual void MergeSettingsToRegistry(SettingsRegistryInterface& registry);
 
         //! Sets the specializations that will be used when loading the Settings Registry. Extend this in derived

Code/Framework/AzCore/AzCore/NativeUI/NativeUIRequests.h

@@ -15,45 +15,49 @@
 #include <AzCore/EBus/EBus.h>
 #include <AzCore/std/string/string.h>
 
-namespace AZ
+namespace AZ::NativeUI
 {
-    namespace NativeUI
+    enum AssertAction
     {
-        enum AssertAction
-        {
-            IGNORE_ASSERT = 0,
-            IGNORE_ALL_ASSERTS,
-            BREAK,
-            NONE,
-        };
+        IGNORE_ASSERT = 0,
+        IGNORE_ALL_ASSERTS,
+        BREAK,
+        NONE,
+    };
 
-        class NativeUIRequests
-            : public AZ::EBusTraits
-        {
-        public:
-            //////////////////////////////////////////////////////////////////////////
-            // EBusTraits overrides
-            static const AZ::EBusHandlerPolicy HandlerPolicy = AZ::EBusHandlerPolicy::Single;
-            static const AZ::EBusAddressPolicy AddressPolicy = AZ::EBusAddressPolicy::Single;
-            using MutexType = AZStd::recursive_mutex;
+    class NativeUIRequests
+    {
+    public:
+        AZ_RTTI(NativeUIRequests, "{48361EE6-C1E7-4965-A13A-7425B2691817}");
+        virtual ~NativeUIRequests() = default;
 
-            // Waits for user to select an option before execution continues
-            // Returns the option string selected by the user
-            virtual AZStd::string DisplayBlockingDialog(const AZStd::string& /*title*/, const AZStd::string& /*message*/, const AZStd::vector<AZStd::string>& /*options*/) const { return ""; };
+        // Waits for user to select an option before execution continues
+        // Returns the option string selected by the user
+        virtual AZStd::string DisplayBlockingDialog(const AZStd::string& /*title*/, const AZStd::string& /*message*/, const AZStd::vector<AZStd::string>& /*options*/) const { return ""; };
 
-            // Waits for user to select an option ('Ok' or optionally 'Cancel') before execution continues
-            // Returns the option string selected by the user
-            virtual AZStd::string DisplayOkDialog(const AZStd::string& /*title*/, const AZStd::string& /*message*/, bool /*showCancel*/) const { return ""; };
+        // Waits for user to select an option ('Ok' or optionally 'Cancel') before execution continues
+        // Returns the option string selected by the user
+        virtual AZStd::string DisplayOkDialog(const AZStd::string& /*title*/, const AZStd::string& /*message*/, bool /*showCancel*/) const { return ""; };
 
-            // Waits for user to select an option ('Yes', 'No' or optionally 'Cancel') before execution continues
-            // Returns the option string selected by the user
-            virtual AZStd::string DisplayYesNoDialog(const AZStd::string& /*title*/, const AZStd::string& /*message*/, bool /*showCancel*/) const { return ""; };
+        // Waits for user to select an option ('Yes', 'No' or optionally 'Cancel') before execution continues
+        // Returns the option string selected by the user
+        virtual AZStd::string DisplayYesNoDialog(const AZStd::string& /*title*/, const AZStd::string& /*message*/, bool /*showCancel*/) const { return ""; };
 
-            // Displays an assert dialog box
-            // Returns the action selected by the user
-            virtual AssertAction DisplayAssertDialog(const AZStd::string& /*message*/) const { return AssertAction::NONE; };
-        };
+        // Displays an assert dialog box
+        // Returns the action selected by the user
+        virtual AssertAction DisplayAssertDialog(const AZStd::string& /*message*/) const { return AssertAction::NONE; };
+    };
 
-        using NativeUIRequestBus = AZ::EBus<NativeUIRequests>;
-    }
-}
+    class NativeUIEBusTraits
+        : public AZ::EBusTraits
+    {
+    public:
+        //////////////////////////////////////////////////////////////////////////
+        // EBusTraits overrides
+        static const AZ::EBusHandlerPolicy HandlerPolicy = AZ::EBusHandlerPolicy::Single;
+        static const AZ::EBusAddressPolicy AddressPolicy = AZ::EBusAddressPolicy::Single;
+        using MutexType = AZStd::recursive_mutex;
+    };
+
+    using NativeUIRequestBus = AZ::EBus<NativeUIRequests, NativeUIEBusTraits>;
+} // namespace AZ::NativeUI

Code/Framework/AzCore/AzCore/NativeUI/NativeUISystemComponent.cpp

@@ -15,50 +15,19 @@
 
 #include <AzCore/NativeUI/NativeUISystemComponent.h>
 
-namespace AZ
+namespace AZ::NativeUI
 {
-    using namespace AZ::NativeUI;
-
-    void NativeUISystemComponent::Reflect(AZ::ReflectContext* context)
+    NativeUISystem::NativeUISystem()
     {
-        if (AZ::SerializeContext* serialize = azrtti_cast<AZ::SerializeContext*>(context))
-        {
-            serialize->Class<NativeUISystemComponent, AZ::Component>()
-                ->Version(0)
-                ;
-
-            if (AZ::EditContext* ec = serialize->GetEditContext())
-            {
-                ec->Class<NativeUISystemComponent>("NativeUI", "Adds basic support for native (platform specific) UI dialog boxes")
-                    ->ClassElement(AZ::Edit::ClassElements::EditorData, "")
-                        ->Attribute(AZ::Edit::Attributes::AppearsInAddComponentMenu, AZ_CRC("System", 0xc94d118b))
-                        ->Attribute(AZ::Edit::Attributes::AutoExpand, true)
-                    ;
-            }
-        }
+        NativeUIRequestBus::Handler::BusConnect();
     }
 
-    void NativeUISystemComponent::GetProvidedServices(AZ::ComponentDescriptor::DependencyArrayType& provided)
+    NativeUISystem::~NativeUISystem()
     {
-        provided.push_back(AZ_CRC("NativeUIService", 0x8ec25f87));
+        NativeUIRequestBus::Handler::BusDisconnect();
     }
 
-    void NativeUISystemComponent::GetIncompatibleServices(AZ::ComponentDescriptor::DependencyArrayType& incompatible)
-    {
-        incompatible.push_back(AZ_CRC("NativeUIService", 0x8ec25f87));
-    }
-
-    void NativeUISystemComponent::GetRequiredServices(AZ::ComponentDescriptor::DependencyArrayType& required)
-    {
-        (void)required;
-    }
-
-    void NativeUISystemComponent::GetDependentServices(AZ::ComponentDescriptor::DependencyArrayType& dependent)
-    {
-        (void)dependent;
-    }
-
-    AssertAction NativeUISystemComponent::DisplayAssertDialog(const AZStd::string& message) const
+    AssertAction NativeUISystem::DisplayAssertDialog(const AZStd::string& message) const
     {
         static const char* buttonNames[3] = { "Ignore", "Ignore All", "Break" };
         AZStd::vector<AZStd::string> options;
@@ -80,7 +49,7 @@ namespace AZ
         return AssertAction::NONE;
     }
 
-    AZStd::string NativeUISystemComponent::DisplayOkDialog(const AZStd::string& title, const AZStd::string& message, bool showCancel) const
+    AZStd::string NativeUISystem::DisplayOkDialog(const AZStd::string& title, const AZStd::string& message, bool showCancel) const
     {
         AZStd::vector<AZStd::string> options;
 
@@ -93,7 +62,7 @@ namespace AZ
         return DisplayBlockingDialog(title, message, options);
     }
 
-    AZStd::string NativeUISystemComponent::DisplayYesNoDialog(const AZStd::string& title, const AZStd::string& message, bool showCancel) const
+    AZStd::string NativeUISystem::DisplayYesNoDialog(const AZStd::string& title, const AZStd::string& message, bool showCancel) const
     {
         AZStd::vector<AZStd::string> options;
 
@@ -106,18 +75,4 @@ namespace AZ
 
         return DisplayBlockingDialog(title, message, options);
     }
-
-    void NativeUISystemComponent::Init()
-    {
-    }
-
-    void NativeUISystemComponent::Activate()
-    {
-        NativeUIRequestBus::Handler::BusConnect();
-    }
-
-    void NativeUISystemComponent::Deactivate()
-    {
-        NativeUIRequestBus::Handler::BusDisconnect();
-    }
-}
+} // namespace AZ::NativeUI

Code/Framework/AzCore/AzCore/NativeUI/NativeUISystemComponent.h

@@ -15,40 +15,24 @@
 #include <AzCore/Component/Component.h>
 #include <AzCore/NativeUI/NativeUIRequests.h>
 
-namespace AZ
+namespace AZ::NativeUI
 {
-    namespace NativeUI
+    class NativeUISystem
+        : public NativeUIRequestBus::Handler
     {
-        class NativeUISystemComponent
-            : public AZ::Component
-            , public NativeUIRequestBus::Handler
-        {
-        public:
-            AZ_COMPONENT(NativeUISystemComponent, "{E996C058-4AFE-4C8C-816F-98D864D8576D}");
+    public:
+        AZ_RTTI(NativeUISystem, "{FF534B2C-11BE-4DEA-A5B7-A4FA96FE1EDE}", NativeUIRequests);
+        AZ_CLASS_ALLOCATOR(NativeUISystem, AZ::OSAllocator, 0);
 
-            static void Reflect(AZ::ReflectContext* context);
+        NativeUISystem();
+        ~NativeUISystem() override;
 
-            static void GetProvidedServices(AZ::ComponentDescriptor::DependencyArrayType& provided);
-            static void GetIncompatibleServices(AZ::ComponentDescriptor::DependencyArrayType& incompatible);
-            static void GetRequiredServices(AZ::ComponentDescriptor::DependencyArrayType& required);
-            static void GetDependentServices(AZ::ComponentDescriptor::DependencyArrayType& dependent);
-
-            ////////////////////////////////////////////////////////////////////////
-            // NativeUIRequestBus interface implementation
-            AZStd::string DisplayBlockingDialog(const AZStd::string& title, const AZStd::string& message, const AZStd::vector<AZStd::string>& options) const override;
-            AZStd::string DisplayOkDialog(const AZStd::string& title, const AZStd::string& message, bool showCancel) const override;
-            AZStd::string DisplayYesNoDialog(const AZStd::string& title, const AZStd::string& message, bool showCancel) const override;
-            AssertAction DisplayAssertDialog(const AZStd::string& message) const override;
-            ////////////////////////////////////////////////////////////////////////
-
-        protected:
-
-            ////////////////////////////////////////////////////////////////////////
-            // AZ::Component interface implementation
-            void Init() override;
-            void Activate() override;
-            void Deactivate() override;
-            ////////////////////////////////////////////////////////////////////////
-        };
-    }
-}
+        ////////////////////////////////////////////////////////////////////////
+        // NativeUIRequestBus interface implementation
+        AZStd::string DisplayBlockingDialog(const AZStd::string& title, const AZStd::string& message, const AZStd::vector<AZStd::string>& options) const override;
+        AZStd::string DisplayOkDialog(const AZStd::string& title, const AZStd::string& message, bool showCancel) const override;
+        AZStd::string DisplayYesNoDialog(const AZStd::string& title, const AZStd::string& message, bool showCancel) const override;
+        AssertAction DisplayAssertDialog(const AZStd::string& message) const override;
+        ////////////////////////////////////////////////////////////////////////
+    };
+} // namespace AZ::NativeUI

Code/Framework/AzCore/AzCore/Script/ScriptSystemComponent.cpp

@@ -699,6 +699,10 @@ Data::AssetHandler::LoadResult ScriptSystemComponent::LoadAssetData(
         script->m_scriptBuffer.resize(scriptDataLength);
         stream->Read(scriptDataLength, script->m_scriptBuffer.data());
 
+        // Clear cached references in the event of a successful load. This function has to be queued on
+        // AssetBus where NotifyAssetReloaded is also queued, to ensure its execution before NotifyAssetReloaded
+        Data::AssetBus::QueueFunction(&ScriptSystemComponent::ClearAssetReferences, this, asset.GetId());
+
         return Data::AssetHandler::LoadResult::LoadComplete;
     }
 

Code/Framework/AzCore/AzCore/Settings/SettingsRegistry.h

@@ -256,7 +256,7 @@ namespace AZ
 
         //! Remove the value at the provided path 
         //! @param path The path to a value that should be removed
-        //! @return Whether or not the value was stored at the provided path. An invalid path will return false;
+        //! @return Whether or not the path was found and removed. An invalid path will return false;
         virtual bool Remove(AZStd::string_view path) = 0;
 
         //! Structure which contains configuration settings for how to parse a single command line argument

Code/Framework/AzCore/AzCore/Settings/SettingsRegistryMergeUtils.cpp

@@ -32,17 +32,12 @@
 namespace AZ::Internal
 {
     AZ::SettingsRegistryInterface::FixedValueString GetEngineMonikerForProject(
-        SettingsRegistryInterface& settingsRegistry, const AZ::IO::FixedMaxPath& projectPath)
+        SettingsRegistryInterface& settingsRegistry, const AZ::IO::FixedMaxPath& projectJsonPath)
     {
         // projectPath needs to be an absolute path here.
         using namespace AZ::SettingsRegistryMergeUtils;
-        bool projectJsonMerged = false;
-        auto projectJsonPath = projectPath / "project.json";
-        if (AZ::IO::SystemFile::Exists(projectJsonPath.c_str()))
-        {
-            projectJsonMerged = settingsRegistry.MergeSettingsFile(
-                projectJsonPath.Native(), AZ::SettingsRegistryInterface::Format::JsonMergePatch, ProjectSettingsRootKey);
-        }
+        bool projectJsonMerged = settingsRegistry.MergeSettingsFile(
+            projectJsonPath.Native(), AZ::SettingsRegistryInterface::Format::JsonMergePatch, ProjectSettingsRootKey);
 
         AZ::SettingsRegistryInterface::FixedValueString engineMoniker;
         if (projectJsonMerged)
@@ -105,12 +100,12 @@ namespace AZ::Internal
 
             const auto engineMonikerKey = AZ::SettingsRegistryInterface::FixedValueString::format("%s/engine_name", EngineSettingsRootKey);
 
+            AZStd::set<AZ::IO::FixedMaxPath> projectPathsNotFound;
+
             for (EngineInfo& engineInfo : pathVisitor.m_enginePaths)
             {
-                AZ::IO::FixedMaxPath engineSettingsPath{engineInfo.m_path};
-                engineSettingsPath /= "engine.json";
-
-                if (AZ::IO::SystemFile::Exists(engineSettingsPath.c_str()))
+                if (auto engineSettingsPath = AZ::IO::FixedMaxPath{engineInfo.m_path} / "engine.json";
+                    AZ::IO::SystemFile::Exists(engineSettingsPath.c_str()))
                 {
                     if (settingsRegistry.MergeSettingsFile(
                             engineSettingsPath.Native(), AZ::SettingsRegistryInterface::Format::JsonMergePatch, EngineSettingsRootKey))
@@ -119,12 +114,61 @@ namespace AZ::Internal
                     }
                 }
 
-                auto engineMoniker = Internal::GetEngineMonikerForProject(settingsRegistry, engineInfo.m_path / projectPath);
-                if (!engineMoniker.empty() && engineMoniker == engineInfo.m_moniker)
+                if (auto projectJsonPath = (engineInfo.m_path / projectPath / "project.json").LexicallyNormal();
+                    AZ::IO::SystemFile::Exists(projectJsonPath.c_str()))
                 {
-                    engineRoot = engineInfo.m_path;
-                    break;
+                    if (auto engineMoniker = Internal::GetEngineMonikerForProject(settingsRegistry, projectJsonPath);
+                        !engineMoniker.empty() && engineMoniker == engineInfo.m_moniker)
+                    {
+                        engineRoot = engineInfo.m_path;
+                        break;
+                    }
                 }
+                else
+                {
+                    projectPathsNotFound.insert(projectJsonPath);
+                }
+
+                // Continue looking for candidates, remove the previous engine and project settings that were merged above.
+                settingsRegistry.Remove(ProjectSettingsRootKey);
+                settingsRegistry.Remove(EngineSettingsRootKey);
+            }
+
+            if (engineRoot.empty())
+            {
+                AZStd::string errorStr;
+                if (!projectPathsNotFound.empty())
+                {
+                    // This case is usually encountered when a project path is given as a relative path,
+                    // which is assumed to be relative to an engine root.
+                    // When no project.json files are found this way, dump this error message about
+                    // which project paths were checked.
+                    AZStd::string projectPathsTested;
+                    for (const auto& path : projectPathsNotFound)
+                    {
+                        projectPathsTested.append(AZStd::string::format("  %s\n", path.c_str()));
+                    }
+                    errorStr = AZStd::string::format("No valid project was found at these locations:\n%s"
+                        "Please supply a valid --project-path to the application.",
+                        projectPathsTested.c_str());
+                }
+                else
+                {
+                    // The other case is that a project.json was found, but after checking all the registered engines
+                    // none of them matched the engine moniker.
+                    AZStd::string enginePathsChecked;
+                    for (const auto& engineInfo : pathVisitor.m_enginePaths)
+                    {
+                        enginePathsChecked.append(AZStd::string::format("  %s (%s)\n", engineInfo.m_path.c_str(), engineInfo.m_moniker.c_str()));
+                    }
+                    errorStr = AZStd::string::format(
+                        "No engine was found in o3de_manifest.json with a name that matches the one set in the project.json.\n"
+                        "Engines that were checked:\n%s"
+                        "Please check that your engine and project have both been registered with scripts/o3de.py.", enginePathsChecked.c_str()
+                    );
+                }
+
+                settingsRegistry.Set(FilePathKey_ErrorText, errorStr.c_str());
             }
         }
 
@@ -158,7 +202,7 @@ namespace AZ::Internal
         return {};
     }
 
-    void InjectSettingToCommandLineFront(AZ::SettingsRegistryInterface& settingsRegistry,
+    void InjectSettingToCommandLineBack(AZ::SettingsRegistryInterface& settingsRegistry,
         AZStd::string_view path, AZStd::string_view value)
     {
         AZ::CommandLine commandLine;
@@ -168,7 +212,7 @@ namespace AZ::Internal
 
         auto projectPathOverride = AZStd::string::format(R"(--regset="%.*s=%.*s")",
             aznumeric_cast<int>(path.size()), path.data(), aznumeric_cast<int>(value.size()), value.data());
-        paramContainer.emplace(paramContainer.begin(), AZStd::move(projectPathOverride));
+        paramContainer.emplace(paramContainer.end(), AZStd::move(projectPathOverride));
         commandLine.Parse(paramContainer);
         AZ::SettingsRegistryMergeUtils::StoreCommandLineToRegistry(settingsRegistry, commandLine);
     }
@@ -197,8 +241,8 @@ namespace AZ::SettingsRegistryMergeUtils
             if (!engineRoot.empty())
             {
                 settingsRegistry.Set(engineRootKey, engineRoot.Native());
-                // Inject the engine root into the front of the command line settings
-                Internal::InjectSettingToCommandLineFront(settingsRegistry, engineRootKey, engineRoot.Native());
+                // Inject the engine root at the end of the command line settings
+                Internal::InjectSettingToCommandLineBack(settingsRegistry, engineRootKey, engineRoot.Native());
                 return engineRoot;
             }
         }
@@ -244,8 +288,8 @@ namespace AZ::SettingsRegistryMergeUtils
             if (!projectRoot.empty())
             {
                 settingsRegistry.Set(projectRootKey, projectRoot.c_str());
-                // Inject the project root into the front of the command line settings
-                Internal::InjectSettingToCommandLineFront(settingsRegistry, projectRootKey, projectRoot.Native());
+                // Inject the project root at the end of the command line settings
+                Internal::InjectSettingToCommandLineBack(settingsRegistry, projectRootKey, projectRoot.Native());
                 return projectRoot;
             }
         }
@@ -874,6 +918,49 @@ namespace AZ::SettingsRegistryMergeUtils
         return true;
     }
 
+    void ParseCommandLine(AZ::CommandLine& commandLine)
+    {
+        struct OptionKeyToRegsetKey
+        {
+            AZStd::string_view m_optionKey;
+            AZStd::string m_regsetKey;
+        };
+
+        // Provide overrides for the engine root, the project root and the project cache root
+        AZStd::array commandOptions = {
+            OptionKeyToRegsetKey{
+                "engine-path", AZStd::string::format("%s/engine_path", AZ::SettingsRegistryMergeUtils::BootstrapSettingsRootKey)},
+            OptionKeyToRegsetKey{
+                "project-path", AZStd::string::format("%s/project_path", AZ::SettingsRegistryMergeUtils::BootstrapSettingsRootKey)},
+            OptionKeyToRegsetKey{
+                "project-cache-path",
+                AZStd::string::format("%s/project_cache_path", AZ::SettingsRegistryMergeUtils::BootstrapSettingsRootKey)}};
+
+        AZStd::fixed_vector<AZStd::string, commandOptions.size()> overrideArgs;
+
+        for (auto&& [optionKey, regsetKey] : commandOptions)
+        {
+            if (size_t optionCount = commandLine.GetNumSwitchValues(optionKey); optionCount > 0)
+            {
+                // Use the last supplied command option value to override previous values
+                auto overrideArg = AZStd::string::format(
+                    R"(--regset="%s=%s")", regsetKey.c_str(), commandLine.GetSwitchValue(optionKey, optionCount - 1).c_str());
+                overrideArgs.emplace_back(AZStd::move(overrideArg));
+            }
+        }
+
+        if (!overrideArgs.empty())
+        {
+            // Dump the input command line, add the additional option overrides
+            // and Parse the new command line args (write back) into the input command line.
+            AZ::CommandLine::ParamContainer commandLineArgs;
+            commandLine.Dump(commandLineArgs);
+            commandLineArgs.insert(
+                commandLineArgs.end(), AZStd::make_move_iterator(overrideArgs.begin()), AZStd::make_move_iterator(overrideArgs.end()));
+            commandLine.Parse(commandLineArgs);
+        }
+    }
+
     bool DumpSettingsRegistryToStream(SettingsRegistryInterface& registry, AZStd::string_view key,
         AZ::IO::GenericStream& stream, const DumperSettings& dumperSettings)
     {

Code/Framework/AzCore/AzCore/Settings/SettingsRegistryMergeUtils.h

@@ -55,6 +55,9 @@ namespace AZ::SettingsRegistryMergeUtils
     //! Development write storage path may be considered temporary or cache storage on some platforms
     inline static constexpr char FilePathKey_DevWriteStorage[] = "/Amazon/AzCore/Runtime/FilePaths/DevWriteStorage";
 
+    //! Stores error text regarding engine boot sequence when engine and project roots cannot be determined
+    inline static constexpr char FilePathKey_ErrorText[] = "/Amazon/AzCore/Runtime/FilePaths/ErrorText";
+
     //! Root key for where command line are stored at within the settings registry
     inline static constexpr char CommandLineRootKey[] = "/Amazon/AzCore/Runtime/CommandLine";
     //! Key set to trigger a notification that the CommandLine has been stored within the settings registry
@@ -219,6 +222,9 @@ namespace AZ::SettingsRegistryMergeUtils
     //! into the AZ::CommandLine instance
     bool GetCommandLineFromRegistry(SettingsRegistryInterface& registry, AZ::CommandLine& commandLine);
 
+    //! Parse a CommandLine and transform certain options into formal "regset" options
+    void ParseCommandLine(AZ::CommandLine& commandLine);
+
     //! Structure for configuring how values should be dumped from the Settings Registry
     struct DumperSettings
     {

Code/Framework/AzCore/Platform/Android/AzCore/NativeUI/NativeUISystemComponent_Android.cpp

@@ -22,7 +22,7 @@ namespace AZ
 {
     namespace NativeUI
     {
-        AZStd::string NativeUISystemComponent::DisplayBlockingDialog(const AZStd::string& title, const AZStd::string& message, const AZStd::vector<AZStd::string>& options) const
+        AZStd::string NativeUISystem::DisplayBlockingDialog(const AZStd::string& title, const AZStd::string& message, const AZStd::vector<AZStd::string>& options) const
         {
             AZ::Android::JNI::Object object("com/amazon/lumberyard/NativeUI/LumberyardNativeUI");
             object.RegisterStaticMethod("DisplayDialog", "(Landroid/app/Activity;Ljava/lang/String;Ljava/lang/String;[Ljava/lang/String;)V");

Code/Framework/AzCore/Platform/Common/Unimplemented/AzCore/NativeUI/NativeUISystemComponent_Unimplemented.cpp

@@ -12,16 +12,11 @@
 
 #include <AzCore/NativeUI/NativeUISystemComponent.h>
 
-namespace AZ
+namespace AZ::NativeUI
 {
-    namespace NativeUI
+    AZStd::string NativeUISystem::DisplayBlockingDialog([[maybe_unused]] const AZStd::string& title, [[maybe_unused]] const AZStd::string& message,
+        [[maybe_unused]] const AZStd::vector<AZStd::string>& options) const
     {
-        AZStd::string NativeUISystemComponent::DisplayBlockingDialog(const AZStd::string& title, const AZStd::string& message, const AZStd::vector<AZStd::string>& options) const
-        {
-            AZ_UNUSED(title);
-            AZ_UNUSED(message);
-            AZ_UNUSED(options);
-            return "";
-        }
+        return {};
     }
 }

Code/Framework/AzCore/Platform/Mac/AzCore/NativeUI/NativeUISystemComponent_Mac.mm

@@ -26,7 +26,7 @@ namespace AZ
 {
     namespace NativeUI
     {
-        AZStd::string NativeUISystemComponent::DisplayBlockingDialog(const AZStd::string& title, const AZStd::string& message, const AZStd::vector<AZStd::string>& options) const
+        AZStd::string NativeUISystem::DisplayBlockingDialog(const AZStd::string& title, const AZStd::string& message, const AZStd::vector<AZStd::string>& options) const
         {
             __block NSModalResponse response = -1;
             

Code/Framework/AzCore/Platform/Windows/AzCore/NativeUI/NativeUISystemComponent_Windows.cpp

@@ -245,7 +245,7 @@ namespace AZ
 {
     namespace NativeUI
     {
-        AZStd::string NativeUISystemComponent::DisplayBlockingDialog(const AZStd::string& title, const AZStd::string& message, const AZStd::vector<AZStd::string>& options) const
+        AZStd::string NativeUISystem::DisplayBlockingDialog(const AZStd::string& title, const AZStd::string& message, const AZStd::vector<AZStd::string>& options) const
         {
             if (options.size() >= MAX_ITEMS)
             {

Code/Framework/AzCore/Platform/iOS/AzCore/NativeUI/NativeUISystemComponent_iOS.mm

@@ -18,7 +18,7 @@ namespace AZ
 {
     namespace NativeUI
     {
-        AZStd::string NativeUISystemComponent::DisplayBlockingDialog(const AZStd::string& title, const AZStd::string& message, const AZStd::vector<AZStd::string>& options) const
+        AZStd::string NativeUISystem::DisplayBlockingDialog(const AZStd::string& title, const AZStd::string& message, const AZStd::vector<AZStd::string>& options) const
         {
             __block AZStd::string userSelection = "";
             

Code/Framework/AzFramework/AzFramework/Application/Application.cpp

@@ -175,7 +175,7 @@ namespace AzFramework
         }
 
         // Initializes the IArchive for reading archive(.pak) files
-        if (auto archive = AZ::Interface<AZ::IO::IArchive>::Get(); !archive)
+        if (auto archive = AZ::Interface<AZ::IO::IArchive>::Get(); archive == nullptr)
         {
             m_archive = AZStd::make_unique<AZ::IO::Archive>();
             AZ::Interface<AZ::IO::IArchive>::Register(m_archive.get());
@@ -189,6 +189,12 @@ namespace AzFramework
             SetFileIOAliases();
         }
 
+        if (auto nativeUI = AZ::Interface<AZ::NativeUI::NativeUIRequests>::Get(); nativeUI == nullptr)
+        {
+            m_nativeUI = AZStd::make_unique<AZ::NativeUI::NativeUISystem>();
+            AZ::Interface<AZ::NativeUI::NativeUIRequests>::Register(m_nativeUI.get());
+        }
+
         ApplicationRequests::Bus::Handler::BusConnect();
         AZ::UserSettingsFileLocatorBus::Handler::BusConnect();
         NetSystemRequestBus::Handler::BusConnect();
@@ -205,12 +211,17 @@ namespace AzFramework
         AZ::UserSettingsFileLocatorBus::Handler::BusDisconnect();
         ApplicationRequests::Bus::Handler::BusDisconnect();
 
+        if (AZ::Interface<AZ::NativeUI::NativeUIRequests>::Get() == m_nativeUI.get())
+        {
+            AZ::Interface<AZ::NativeUI::NativeUIRequests>::Unregister(m_nativeUI.get());
+        }
+        m_nativeUI.reset();
+
         // Unset the Archive file IO if it is set as the direct instance
         if (AZ::IO::FileIOBase::GetInstance() == m_archiveFileIO.get())
         {
             AZ::IO::FileIOBase::SetInstance(nullptr);
         }
-
         m_archiveFileIO.reset();
 
         // Destroy the IArchive instance
@@ -303,7 +314,6 @@ namespace AzFramework
             azrtti_typeid<AZ::AssetManagerComponent>(),
             azrtti_typeid<AZ::UserSettingsComponent>(),
             azrtti_typeid<AZ::Debug::FrameProfilerComponent>(),
-            azrtti_typeid<AZ::NativeUI::NativeUISystemComponent>(),
             azrtti_typeid<AZ::SliceComponent>(),
             azrtti_typeid<AZ::SliceSystemComponent>(),
 
@@ -372,7 +382,6 @@ namespace AzFramework
             azrtti_typeid<AZ::UserSettingsComponent>(),
             azrtti_typeid<AZ::ScriptSystemComponent>(),
             azrtti_typeid<AZ::JobManagerComponent>(),
-            azrtti_typeid<AZ::NativeUI::NativeUISystemComponent>(),
             azrtti_typeid<AZ::SliceSystemComponent>(),
 
             azrtti_typeid<AzFramework::AssetCatalogComponent>(),

Code/Framework/AzFramework/AzFramework/Application/Application.h

@@ -16,6 +16,7 @@
 #include <AzCore/Component/ComponentApplication.h>
 #include <AzCore/UserSettings/UserSettings.h>
 #include <AzCore/Math/Uuid.h>
+#include <AzCore/NativeUI/NativeUIRequests.h>
 #include <AzCore/IO/SystemFile.h>
 #include <AzCore/std/smart_ptr/unique_ptr.h>
 #include <AzCore/std/string/fixed_string.h>
@@ -187,6 +188,7 @@ namespace AzFramework
         AZStd::unique_ptr<AZ::IO::FileIOBase> m_archiveFileIO; ///> The Default file IO instance is a ArchiveFileIO.
         AZStd::unique_ptr<AZ::IO::Archive> m_archive; ///> The AZ::IO::Instance
         AZStd::unique_ptr<Implementation> m_pimpl;
+        AZStd::unique_ptr<AZ::NativeUI::NativeUIRequests> m_nativeUI;
         bool m_ownsConsole = false;
 
         bool m_exitMainLoopRequested = false;

Code/Framework/AzFramework/AzFramework/Asset/AssetSystemComponentHelper.cpp

@@ -220,7 +220,7 @@ namespace AzFramework
             {
                 // Read the wait for connection boolean from the Settings Registry
                 AZ::s64 waitForConnect64{};
-                if (!AZ::SettingsRegistryMergeUtils::PlatformGet(*settingsRegistry, waitForConnect64, AZ::SettingsRegistryMergeUtils::BootstrapSettingsRootKey, AzFramework::AssetSystem::WaitForConnect))
+                if (AZ::SettingsRegistryMergeUtils::PlatformGet(*settingsRegistry, waitForConnect64, AZ::SettingsRegistryMergeUtils::BootstrapSettingsRootKey, AzFramework::AssetSystem::WaitForConnect))
                 {
                     outputConnectionSettings.m_waitForConnect = waitForConnect64 != 0;
                 }

Code/Framework/AzFramework/AzFramework/Components/AzFrameworkConfigurationSystemComponent.cpp

@@ -17,7 +17,7 @@
 #include <AzCore/RTTI/BehaviorContext.h>
 #include <AzCore/Debug/Trace.h>
 #include <AzFramework/Scene/Scene.h>
-#include <AzFramework/Scene/SceneSystemBus.h>
+#include <AzFramework/Scene/SceneSystemInterface.h>
 #include <AzFramework/Entity/GameEntityContextComponent.h>
 
 namespace AzFramework
@@ -50,36 +50,34 @@ namespace AzFramework
 
     void AzFrameworkConfigurationSystemComponent::Activate()
     {
-        // Create the defaults scene and associate the GameEntityContext with it.
-        AZ::Outcome<Scene*, AZStd::string> createSceneOutcome = AZ::Failure<AZStd::string>("SceneSystemRequests bus not responding.");
-        SceneSystemRequestBus::BroadcastResult(createSceneOutcome, &AzFramework::SceneSystemRequests::CreateScene, "default");
+        AZ::Outcome<AZStd::shared_ptr<Scene>, AZStd::string> createSceneOutcome =
+            SceneSystemInterface::Get()->CreateScene(Scene::MainSceneName);
         if (createSceneOutcome)
         {
-            Scene* scene = createSceneOutcome.GetValue();
-            bool success = false;
-            EntityContextId gameEntityContextId = EntityContextId::CreateNull();
-            GameEntityContextRequestBus::BroadcastResult(gameEntityContextId, &GameEntityContextRequests::GetGameEntityContextId);
-
-            if (!gameEntityContextId.IsNull())
+            AZStd::shared_ptr<Scene> scene = createSceneOutcome.TakeValue();
+            EntityContext* gameEntityContext = nullptr;
+            GameEntityContextRequestBus::BroadcastResult(gameEntityContext, &GameEntityContextRequests::GetGameEntityContextInstance);
+            if (gameEntityContext != nullptr)
             {
-                SceneSystemRequestBus::BroadcastResult(success, &AzFramework::SceneSystemRequests::SetSceneForEntityContextId, gameEntityContextId, scene);
+                [[maybe_unused]] bool result = scene->SetSubsystem<EntityContext::SceneStorageType&>(gameEntityContext);
+                AZ_Assert(result, "Unable to register main entity context with the main scene.");
+            }
+            else
+            {
+                AZ_Assert(false, "Unable to retrieve the game entity context instance.");
             }
-            AZ_Assert(success, "The application was unable to setup a scene for the game entity context, this should always work");
         }
         else
         {
-            AZ_Assert(false, "%s", createSceneOutcome.GetError().data());
+            AZ_Assert(false, "Unable to create main scene due to: %s", createSceneOutcome.GetError().c_str());
         }
 
     }
 
     void AzFrameworkConfigurationSystemComponent::Deactivate()
     {
-        bool success = false;
-        SceneSystemRequestBus::BroadcastResult(
-            success, &AzFramework::SceneSystemRequestBus::Events::RemoveScene, "default");
-
-        AZ_Assert(success, "\"default\" scene was not removed");
+        [[maybe_unused]] bool success = SceneSystemInterface::Get()->RemoveScene(Scene::MainSceneName);
+        AZ_Assert(success, "Unable to remove the main scene.");
     }
 
     void AzFrameworkConfigurationSystemComponent::GetProvidedServices(AZ::ComponentDescriptor::DependencyArrayType& provided)

Code/Framework/AzFramework/AzFramework/Entity/EntityContext.cpp

@@ -18,6 +18,8 @@
 #include <AzCore/Component/TickBus.h>
 #include <AzCore/Debug/Profiler.h>
 #include <AzCore/std/containers/stack.h>
+#include <AzFramework/Scene/Scene.h>
+#include <AzFramework/Scene/SceneSystemInterface.h>
 
 #include "EntityContext.h"
 
@@ -37,6 +39,30 @@ namespace AzFramework
         }
     }
 
+    AZStd::shared_ptr<Scene> EntityContext::FindContainingScene(const EntityContextId& contextId)
+    {
+        auto sceneSystem = SceneSystemInterface::Get();
+        AZ_Assert(sceneSystem, "Attempting to retrieve the scene containing a entity context before the scene system is available.");
+
+        AZStd::shared_ptr<Scene> result;
+        sceneSystem->IterateActiveScenes([&result, &contextId](const AZStd::shared_ptr<Scene>& scene)
+            {
+                EntityContext** entityContext = scene->FindSubsystemInScene<EntityContext::SceneStorageType>();
+                if (entityContext && (*entityContext)->GetContextId() == contextId)
+                {
+                    result = scene;
+                    // Result found, returning.
+                    return false;
+                }
+                else
+                {
+                    // No match, continuing to search for containing scene.
+                    return true;
+                }
+            });
+        return result;
+    }
+
     //=========================================================================
     // EntityContext ctor
     //=========================================================================

Code/Framework/AzFramework/AzFramework/Entity/EntityContext.h

@@ -17,6 +17,7 @@
 #include <AzCore/Component/EntityBus.h>
 #include <AzCore/Serialization/ObjectStream.h>
 #include <AzCore/Serialization/IdUtils.h>
+#include <AzCore/std/smart_ptr/shared_ptr.h>
 #include <AzFramework/Entity/EntityContextBus.h>
 #include <AzFramework/Entity/SliceEntityOwnershipService.h>
 
@@ -27,7 +28,7 @@ namespace AZ
 
 namespace AzFramework
 {
-    class EntityContext;
+    class Scene;
 
     /**
      * Provides services for a group of entities under the umbrella of a given context.
@@ -47,9 +48,11 @@ namespace AzFramework
         , public EntityOwnershipServiceNotificationBus::Handler
     {
     public:
-
         AZ_TYPE_INFO(EntityContext, "{4F98A6B9-C7B5-450E-8A8A-30EEFC411EF5}");
 
+        /// The type used to store entity in AzFramework::Scene.
+        using SceneStorageType = EntityContext*;
+
         EntityContext(AZ::SerializeContext* serializeContext = nullptr);
         EntityContext(const EntityContextId& contextId, AZ::SerializeContext* serializeContext = nullptr);
         EntityContext(const EntityContextId& contextId, AZStd::unique_ptr<EntityOwnershipService> entityOwnershipService,
@@ -75,6 +78,7 @@ namespace AzFramework
         //////////////////////////////////////////////////////////////////////////
 
         static void Reflect(AZ::ReflectContext* context);
+        static AZStd::shared_ptr<Scene> FindContainingScene(const EntityContextId& contextId);
 
     protected:
 

Code/Framework/AzFramework/AzFramework/Entity/GameEntityContextBus.h

@@ -66,6 +66,8 @@ namespace AzFramework
          */
         virtual EntityContextId GetGameEntityContextId() = 0;
 
+        virtual EntityContext* GetGameEntityContextInstance() = 0;
+
         /**
          * Creates an entity in the game context.
          * @param name A name for the new entity.

Code/Framework/AzFramework/AzFramework/Entity/GameEntityContextComponent.h

@@ -51,6 +51,7 @@ namespace AzFramework
         //////////////////////////////////////////////////////////////////////////
         // GameEntityContextRequestBus
         AZ::Uuid GetGameEntityContextId() override { return GetContextId(); }
+        EntityContext* GetGameEntityContextInstance() override { return this; }
         void ResetGameContext() override;
         AZ::Entity* CreateGameEntity(const char* name) override;
         BehaviorEntity CreateGameEntityForBehaviorContext(const char* name) override;

Code/Framework/AzFramework/AzFramework/ProjectManager/ProjectManager.cpp

@@ -41,9 +41,10 @@ namespace AzFramework::ProjectManager
             // at the end of the function
             AZ::CommandLine commandLine;
             commandLine.Parse(argc, argv);
-            AZ::SettingsRegistryImpl settingsRegistry;
-            // Store the Command line to the Setting Registry
+            AZ::SettingsRegistryMergeUtils::ParseCommandLine(commandLine);
 
+            // Store the Command line to the Setting Registry
+            AZ::SettingsRegistryImpl settingsRegistry;
             AZ::SettingsRegistryMergeUtils::StoreCommandLineToRegistry(settingsRegistry, commandLine);
             AZ::SettingsRegistryMergeUtils::MergeSettingsToRegistry_Bootstrap(settingsRegistry);
             AZ::SettingsRegistryMergeUtils::MergeSettingsToRegistry_O3deUserRegistry(settingsRegistry, AZ_TRAIT_OS_PLATFORM_CODENAME, {});
@@ -68,7 +69,14 @@ namespace AzFramework::ProjectManager
         // If we were able to locate a path to a project, we're done
         if (!projectRootPath.empty())
         {
-            return ProjectPathCheckResult::ProjectPathFound;
+            AZ::IO::FixedMaxPath projectJsonPath = engineRootPath / projectRootPath / "project.json";
+            if (AZ::IO::SystemFile::Exists(projectJsonPath.c_str()))
+            {
+                return ProjectPathCheckResult::ProjectPathFound;
+            }
+            AZ_TracePrintf(
+                "ProjectManager", "Did not find a project file at location '%s', launching the Project Manager...",
+                projectJsonPath.c_str());
         }
 
         if (LaunchProjectManager(engineRootPath))

Code/Framework/AzFramework/AzFramework/Render/Intersector.cpp

@@ -14,9 +14,9 @@
 #include <AzCore/std/algorithm.h>
 #include <AzCore/std/sort.h>
 
+#include <AzFramework/Entity/EntityContext.h>
 #include <AzFramework/Render/Intersector.h>
 #include <AzFramework/Scene/Scene.h>
-#include <AzFramework/Scene/SceneSystemBus.h>
 #include <AzFramework/Visibility/BoundsBus.h>
 
 #include <algorithm>
@@ -30,11 +30,11 @@ namespace AzFramework
         {
             IntersectorBus::Handler::BusConnect(m_contextId);
             IntersectionNotificationBus::Handler::BusConnect(m_contextId);
-            Scene* scene = nullptr;
-            SceneSystemRequestBus::BroadcastResult(scene, &AzFramework::SceneSystemRequestBus::Events::GetSceneFromEntityContextId, m_contextId);
+
+            AZStd::shared_ptr<Scene> scene = EntityContext::FindContainingScene(m_contextId);
             if (scene)
             {
-                scene->SetSubsystem<IntersectorInterface>(this);
+                scene->SetSubsystem(this);
             }
         }
 
@@ -42,11 +42,12 @@ namespace AzFramework
         {
             IntersectorBus::Handler::BusDisconnect();
             IntersectionNotificationBus::Handler::BusDisconnect();
-            Scene* scene = nullptr;
-            SceneSystemRequestBus::BroadcastResult(scene, &AzFramework::SceneSystemRequestBus::Events::GetSceneFromEntityContextId, m_contextId);
+
+            AZStd::shared_ptr<Scene> scene = EntityContext::FindContainingScene(m_contextId);
             if (scene)
             {
-                scene->UnsetSubsystem<IntersectorInterface>();
+                [[maybe_unused]] bool result = scene->UnsetSubsystem(this);
+                AZ_Assert(result, "Failed to unregister Intersector with scene");
             }
         }
 

Code/Framework/AzFramework/AzFramework/Render/Intersector.h

@@ -33,6 +33,8 @@ namespace AzFramework
             , protected IntersectionNotificationBus::Handler
         {
         public:
+            AZ_TYPE_INFO(AzFramework::RenderGeometry::Intersector, "{4CCA7971-CD83-4856-ADEA-89CEB41FB197}");
+
             Intersector(AzFramework::EntityContextId contextId);
             ~Intersector();
 

Code/Framework/AzFramework/AzFramework/Scene/Scene.cpp

@@ -14,13 +14,102 @@
 
 namespace AzFramework
 {
-    Scene::Scene(AZStd::string_view name)
-        : m_name(name)
+    Scene::Scene(AZStd::string name)
+        : m_name(AZStd::move(name))
     {
     }
 
-    const AZStd::string& Scene::GetName()
+    Scene::Scene(AZStd::string name, AZStd::shared_ptr<Scene> parent)
+        : m_name(AZStd::move(name))
+        , m_parent(AZStd::move(parent))
+    {
+    }
+
+    Scene::~Scene()
+    {
+        m_removalEvent.Signal(*this, RemovalEventType::Destroyed);
+    }
+
+    const AZStd::string& Scene::GetName() const
     {
         return m_name;
     }
+
+    const AZStd::shared_ptr<Scene>& Scene::GetParent()
+    {
+        return m_parent;
+    }
+
+    AZStd::shared_ptr<const Scene> Scene::GetParent() const
+    {
+        return m_parent;
+    }
+
+    bool Scene::IsAlive() const
+    {
+        return m_isAlive;
+    }
+
+    void Scene::ConnectToEvents(RemovalEvent::Handler& handler)
+    {
+        handler.Connect(m_removalEvent);
+    }
+
+    void Scene::ConnectToEvents(SubsystemEvent::Handler& handler)
+    {
+        handler.Connect(m_subsystemEvent);
+    }
+
+    AZStd::any* Scene::FindSubsystem(const AZ::TypeId& typeId)
+    {
+        AZStd::any* result = FindSubsystemInScene(typeId);
+        return (!result && m_parent) ? m_parent->FindSubsystem(typeId) : result;
+    }
+
+    const AZStd::any* Scene::FindSubsystem(const AZ::TypeId& typeId) const
+    {
+        return const_cast<Scene*>(this)->FindSubsystem(typeId);
+    }
+
+    AZStd::any* Scene::FindSubsystemInScene(const AZ::TypeId& typeId)
+    {
+        // Spot check that the internal arrays remain consistent.
+        AZ_Assert(
+            m_systemKeys.size() == m_systemObjects.size(), "Key and object list in AzFramework::Scene '%s' have gone out of sync.",
+            m_name.c_str());
+
+        const size_t m_systemKeysCount = m_systemKeys.size();
+        for (size_t i = 0; i < m_systemKeysCount; ++i)
+        {
+            if (m_systemKeys[i] != typeId)
+            {
+                continue;
+            }
+            else
+            {
+                return &m_systemObjects[i];
+            }
+        }
+        return nullptr;
+    }
+
+    const AZStd::any* Scene::FindSubsystemInScene(const AZ::TypeId& typeId) const
+    {
+        return const_cast<Scene*>(this)->FindSubsystemInScene(typeId);
+    }
+
+    void Scene::MarkForDestruction()
+    {
+        m_isAlive = false;
+        m_removalEvent.Signal(*this, RemovalEventType::Zombified);
+    }
+
+    void Scene::RemoveSubsystem(size_t index, const AZ::TypeId& subsystemType)
+    {
+        m_systemKeys[index] = m_systemKeys.back();
+        m_systemObjects[index] = AZStd::move(m_systemObjects.back());
+        m_systemKeys.pop_back();
+        m_systemObjects.pop_back();
+        m_subsystemEvent.Signal(*this, SubsystemEventType::Removed, subsystemType);
+    }
 }

Code/Framework/AzFramework/AzFramework/Scene/Scene.h

@@ -11,10 +11,14 @@
  */
 #pragma once
 
+#include <AzCore/EBus/Event.h>
 #include <AzCore/RTTI/RTTI.h>
 #include <AzCore/std/string/string.h>
 #include <AzCore/Memory/SystemAllocator.h>
+#include <AzCore/std/any.h>
 #include <AzCore/std/containers/vector.h>
+#include <AzCore/std/smart_ptr/shared_ptr.h>
+#include <AzCore/std/string/string_view.h>
 
 namespace AzFramework
 {
@@ -24,71 +28,100 @@ namespace AzFramework
         AZ_TYPE_INFO(Scene, "{DB449BB3-7A95-434D-BC61-47ACBB1F3436}");
         AZ_CLASS_ALLOCATOR(Scene, AZ::SystemAllocator, 0);
 
-        explicit Scene(AZStd::string_view name);
+        friend class ISceneSystem;
 
-        const AZStd::string& GetName();
+        constexpr static AZStd::string_view MainSceneName = "Main";
+        constexpr static AZStd::string_view EditorMainSceneName = "Editor";
+
+        enum class RemovalEventType
+        {
+            Zombified, // The scene has be marked for destruction and is no longer visible in the scene system.
+            Destroyed, // The scene has been destroyed.
+        };
+        using RemovalEvent = AZ::Event<Scene&, RemovalEventType>;
+        enum class SubsystemEventType
+        {
+            Added,
+            Removed
+        };
+        using SubsystemEvent = AZ::Event<Scene&, SubsystemEventType, const AZ::TypeId&>;
+
+        explicit Scene(AZStd::string name);
+        Scene(AZStd::string name, AZStd::shared_ptr<Scene> parent);
+        ~Scene();
+
+        [[nodiscard]] const AZStd::string& GetName() const;
+
+        [[nodiscard]] const AZStd::shared_ptr<Scene>& GetParent();
+        [[nodiscard]] AZStd::shared_ptr<const Scene> GetParent() const;
+
+        [[nodiscard]] bool IsAlive() const;
+
+        void ConnectToEvents(RemovalEvent::Handler& handler);
+        void ConnectToEvents(SubsystemEvent::Handler& handler);
         
         // Set the instance of a subsystem associated with this scene.
         template <typename T>
-        bool SetSubsystem(T* system);
+        bool SetSubsystem(T&& system);
 
         // Unset the instance of a subsystem associated with this scene.
         template <typename T>
         bool UnsetSubsystem();
 
-        // Get the instance of a subsystem associated with this scene.
+        // Unset the instance of the exact system associated with this scene.
+        // Use this to make sure the expected instance is removed or to make sure type deduction is done in the same way as during setting.
+        template<typename T>
+        bool UnsetSubsystem(const T& system);
+
+        // Get the instance of a subsystem associated with this scene. This call will also look in parent scenes if not found on the target
+        // scene. Returns a pointer to the subsystem if found, otherwise returns a nullptr.
+        [[nodiscard]] AZStd::any* FindSubsystem(const AZ::TypeId& typeId);
+        // Get the instance of a subsystem associated with this scene. This call will also look in parent scenes if not found on the target
+        // scene. Returns a pointer to the subsystem if found, otherwise returns a nullptr.
+        [[nodiscard]] const AZStd::any* FindSubsystem(const AZ::TypeId& typeId) const;
+        // Get the instance of a subsystem associated with this scene. This call will also look in parent scenes if not found on the target
+        // scene. Returns a pointer to the subsystem if found, otherwise returns a nullptr.
         template <typename T>
-        T* GetSubsystem();
+        [[nodiscard]] T* FindSubsystem();
+        // Get the instance of a subsystem associated with this scene. This call will also look in parent scenes if not found on the target
+        // scene. Returns a pointer to the subsystem if found, otherwise returns a nullptr.
+        template<typename T>
+        [[nodiscard]] const T* FindSubsystem() const;
+
+        // Get the instance of a subsystem associated with this scene. This call will only look in the selected scene. Returns a pointer to
+        // the subsystem if found, otherwise returns a nullptr.
+        [[nodiscard]] AZStd::any* FindSubsystemInScene(const AZ::TypeId& typeId);
+        // Get the instance of a subsystem associated with this scene. This call will only look in the selected scene. Returns a pointer to
+        // the subsystem if found, otherwise returns a nullptr.
+        [[nodiscard]] const AZStd::any* FindSubsystemInScene(const AZ::TypeId& typeId) const;
+        // Get the instance of a subsystem associated with this scene. This call will only look in the selected scene. Returns a pointer to
+        // the subsystem if found, otherwise returns a nullptr.
+        template<typename T>
+        [[nodiscard]] T* FindSubsystemInScene();
+        // Get the instance of a subsystem associated with this scene. This call will only look in the selected scene. Returns a pointer to
+        // the subsystem if found, otherwise returns a nullptr.
+        template<typename T>
+        [[nodiscard]] const T* FindSubsystemInScene() const;
 
     private:
+        void MarkForDestruction();
+        void RemoveSubsystem(size_t index, const AZ::TypeId& subsystemType);
 
-        AZStd::string m_name;
+        RemovalEvent m_removalEvent;
+        SubsystemEvent m_subsystemEvent;
 
         // Storing keys separate from data to optimize for fast key search.
         AZStd::vector<AZ::TypeId> m_systemKeys;
-        AZStd::vector<void*> m_systemPointers;
+        AZStd::vector<AZStd::any> m_systemObjects;
+
+        // Name that identifies the scene.
+        AZStd::string m_name;
+        // Parent to this scene. Any subsystems are inherited from the parent but can be overwritten locally.
+        AZStd::shared_ptr<Scene> m_parent;
+        // If false, the scene has been removed from scene system and can no longer be found. As soon as all handles to the scene are
+        // released it will be destroyed.
+        bool m_isAlive{ true };
     };
-    
-    template <typename T>
-    bool Scene::SetSubsystem(T* system)
-    {
-        if (GetSubsystem<T>() != nullptr)
-        {
-            return false;
-        }
-        m_systemKeys.push_back(T::RTTI_Type());
-        m_systemPointers.push_back(system);
-        return true;
-    }
-
-    template <typename T>
-    bool Scene::UnsetSubsystem()
-    {
-        for (size_t i = 0; i < m_systemKeys.size(); ++i)
-        {
-            if (m_systemKeys.at(i) == T::RTTI_Type())
-            {
-                m_systemKeys.at(i) = m_systemKeys.back();
-                m_systemKeys.pop_back();
-                m_systemPointers.at(i) = m_systemPointers.back();
-                m_systemPointers.pop_back();
-                return true;
-            }
-        }
-        return false;
-    }
-
-    template <typename T>
-    T* Scene::GetSubsystem()
-    {
-        for (size_t i = 0; i < m_systemKeys.size(); ++i)
-        {
-            if (m_systemKeys.at(i) == T::RTTI_Type())
-            {
-                return reinterpret_cast<T*>(m_systemPointers.at(i));
-            }
-        }
-        return nullptr;
-    }
-
 } // AzFramework
+
+#include <AzFramework/Scene/Scene.inl>

Code/Framework/AzFramework/AzFramework/Scene/Scene.inl

@@ -0,0 +1,108 @@
+/*
+ * All or portions of this file Copyright (c) Amazon.com, Inc. or its affiliates or
+ * its licensors.
+ *
+ * For complete copyright and license terms please see the LICENSE at the root of this
+ * distribution (the "License"). All use of this software is governed by the License,
+ * or, if provided, by the license below or the license accompanying this file. Do not
+ * remove or modify any license notices. This file is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *
+ */
+
+namespace AzFramework
+{
+    template<typename T>
+    bool Scene::SetSubsystem(T&& system)
+    {
+        const AZ::TypeId& targetType = azrtti_typeid<T>();
+        for (const AZ::TypeId& key : m_systemKeys)
+        {
+            if (key == targetType)
+            {
+                return false;
+            }
+        }
+
+        m_systemKeys.push_back(targetType);
+        m_systemObjects.emplace_back(AZStd::forward<T>(system));
+        m_subsystemEvent.Signal(*this, SubsystemEventType::Added, targetType);
+        return true;
+    }
+
+    template<typename T>
+    bool Scene::UnsetSubsystem()
+    {
+        const AZ::TypeId& targetType = azrtti_typeid<T>();
+        const size_t m_systemKeysCount = m_systemKeys.size();
+        for (size_t i = 0; i < m_systemKeysCount; ++i)
+        {
+            if (m_systemKeys[i] != targetType)
+            {
+                continue;
+            }
+            else
+            {
+                RemoveSubsystem(i, targetType);
+                return true;
+            }
+        }
+        return false;
+    }
+
+    template<typename T>
+    bool Scene::UnsetSubsystem(const T& system)
+    {
+        const AZ::TypeId& targetType = azrtti_typeid<T>();
+        const size_t systemKeysCount = m_systemKeys.size();
+        for (size_t i = 0; i < systemKeysCount; ++i)
+        {
+            if (m_systemKeys[i] != targetType)
+            {
+                continue;
+            }
+            else
+            {
+                [[maybe_unused]] T* instance = AZStd::any_cast<T>(&m_systemObjects[i]);
+                AZ_Assert(
+                    instance && *instance == system,
+                    "Subsystem being released matched type, but wasn't pointing to the same system that was stored.");
+                RemoveSubsystem(i, targetType);
+                return true;
+            }
+        }
+        return false;
+    }
+
+    template<typename T>
+    T* Scene::FindSubsystem()
+    {
+        const AZ::TypeId& targetType = azrtti_typeid<T>();
+        AZStd::any* subSystem = FindSubsystem(targetType);
+        return subSystem ? AZStd::any_cast<T>(subSystem) : nullptr;
+    }
+
+    template<typename T>
+    const T* Scene::FindSubsystem() const
+    {
+        const AZ::TypeId& targetType = azrtti_typeid<T>();
+        const AZStd::any* subSystem = FindSubsystem(targetType);
+        return subSystem ? AZStd::any_cast<const T>(subSystem) : nullptr;
+    }
+
+    template<typename T>
+    T* Scene::FindSubsystemInScene()
+    {
+        const AZ::TypeId& targetType = azrtti_typeid<T>();
+        AZStd::any* subSystem = FindSubsystemInScene(targetType);
+        return subSystem ? AZStd::any_cast<T>(subSystem) : nullptr;
+    }
+
+    template<typename T>
+    const T* Scene::FindSubsystemInScene() const
+    {
+        const AZ::TypeId& targetType = azrtti_typeid<T>();
+        const AZStd::any* subSystem = FindSubsystemInScene(targetType);
+        return subSystem ? AZStd::any_cast<const T>(subSystem) : nullptr;
+    }
+} // namespace AzFramework

Code/Framework/AzFramework/AzFramework/Scene/SceneSystemBus.h

@@ -1,114 +0,0 @@
-/*
- * All or portions of this file Copyright (c) Amazon.com, Inc. or its affiliates or
- * its licensors.
- *
- * For complete copyright and license terms please see the LICENSE at the root of this
- * distribution (the "License"). All use of this software is governed by the License,
- * or, if provided, by the license below or the license accompanying this file. Do not
- * remove or modify any license notices. This file is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- *
- */
-#pragma once
-
-#include <AzCore/EBus/EBus.h>
-#include <AzFramework/Entity/EntityContext.h>
-
-namespace AzFramework
-{
-    // Forward declarations
-    class Scene;
-
-    //! Interface used to create, get, or destroy scenes.
-    class SceneSystemRequests
-        : public AZ::EBusTraits
-    {
-    public:
-
-        virtual ~SceneSystemRequests() = default;
-
-        //! Single handler policy since there should only be one instance of this system component.
-        static const AZ::EBusHandlerPolicy HandlerPolicy = AZ::EBusHandlerPolicy::Single;
-
-        //! Creates a scene with a given name.
-        //!  - If there is already a scene with the provided name this will return AZ::Failure(). 
-        //!  - If isDefault is set to true and there is already a default scene, the default scene will be switched to this one. 
-        virtual AZ::Outcome<Scene*, AZStd::string> CreateScene(AZStd::string_view name) = 0;
-
-        //! Gets a scene with a given name
-        //!  - If a scene does not exist with the given name, nullptr is returned.
-        virtual Scene* GetScene(AZStd::string_view name) = 0;
-
-        //! Gets all the scenes that currently exist.
-        virtual AZStd::vector<Scene*> GetAllScenes() = 0;
-
-        //! Remove a scene with a given name and return if the operation was successful.
-        //!  - If the removed scene is the default scene, there will no longer be a default scene.
-        virtual bool RemoveScene(AZStd::string_view name) = 0;
-
-        //! Add a mapping from the provided EntityContextId to a Scene
-        //! - If a scene is already associated with this EntityContextId, nothing is changed and false is returned.
-        virtual bool SetSceneForEntityContextId(EntityContextId entityContextId, Scene* scene) = 0;
-
-        //! Remove a mapping from the provided EntityContextId to a Scene
-        //!  - If no scene is found from the provided EntityContextId, false is returned.
-        virtual bool RemoveSceneForEntityContextId(EntityContextId entityContextId, Scene* scene) = 0;
-
-        //! Get the scene associated with an EntityContextId
-        //!  - If no scene is found for the provided EntityContextId, nullptr is returned.
-        virtual Scene* GetSceneFromEntityContextId(EntityContextId entityContextId) = 0;
-    };
-
-    using SceneSystemRequestBus = AZ::EBus<SceneSystemRequests>;
-
-    //! Interface used for notifications from the scene system
-    class SceneSystemNotifications
-        : public AZ::EBusTraits
-    {
-    public:
-
-        virtual ~SceneSystemNotifications() = default;
-
-        //! There can be multiple listeners to changes in the scene system.
-        static const AZ::EBusHandlerPolicy HandlerPolicy = AZ::EBusHandlerPolicy::Multiple;
-
-        //! Called when a scene has been created.
-        virtual void SceneCreated(Scene& /*scene*/) {};
-
-        //! Called just before a scene is removed.
-        virtual void SceneAboutToBeRemoved(Scene& /*scene*/) {};
-
-    };
-
-    using SceneSystemNotificationBus = AZ::EBus<SceneSystemNotifications>;
-
-    //! Interface used for notifications about individual scenes
-    class SceneNotifications
-        : public AZ::EBusTraits
-    {
-    public:
-
-        virtual ~SceneNotifications() = default;
-
-        //! There can be multiple listeners to changes in the scene system.
-        static const AZ::EBusHandlerPolicy HandlerPolicy = AZ::EBusHandlerPolicy::Multiple;
-
-        //! Bus is listened to using the pointer of the scene
-        static const AZ::EBusAddressPolicy AddressPolicy = AZ::EBusAddressPolicy::ById;
-
-        //! Specifies that events are addressed by the pointer to the scene
-        using BusIdType = Scene*;
-
-        //! Called just before a scene is removed.
-        virtual void SceneAboutToBeRemoved() {};
-
-        //! Called when an entity context is mapped to this scene.
-        virtual void EntityContextMapped(EntityContextId /*entityContextId*/) {};
-
-        //! Called when an entity context is unmapped from this scene.
-        virtual void EntityContextUnmapped(EntityContextId /*entityContextId*/) {};
-    };
-
-    using SceneNotificationBus = AZ::EBus<SceneNotifications>;
-
-} // AzFramework

Code/Framework/AzFramework/AzFramework/Scene/SceneSystemComponent.cpp

@@ -14,7 +14,7 @@
 
 #include <AzCore/Serialization/SerializeContext.h>
 #include <AzCore/Serialization/EditContext.h>
-#include <AzFramework/Scene/Scene.h>
+#include <AzCore/std/smart_ptr/make_shared.h>
 
 namespace AzFramework
 {
@@ -41,14 +41,10 @@ namespace AzFramework
 
     void SceneSystemComponent::Activate()
     {
-        // Connect busses
-        SceneSystemRequestBus::Handler::BusConnect();
     }
 
     void SceneSystemComponent::Deactivate()
     {
-        // Disconnect Busses
-        SceneSystemRequestBus::Handler::BusDisconnect();
     }
 
     void SceneSystemComponent::GetProvidedServices(AZ::ComponentDescriptor::DependencyArrayType& provided)
@@ -61,140 +57,105 @@ namespace AzFramework
         incompatible.push_back(AZ_CRC("SceneSystemComponentService", 0xd8975435));
     }
 
-    AZ::Outcome<Scene*, AZStd::string> SceneSystemComponent::CreateScene(AZStd::string_view name)
+    AZ::Outcome<AZStd::shared_ptr<Scene>, AZStd::string> SceneSystemComponent::CreateScene(AZStd::string_view name)
     {
-        Scene* existingScene = GetScene(name);
+        return CreateSceneWithParent(name, nullptr);
+    }
 
+    AZ::Outcome<AZStd::shared_ptr<Scene>, AZStd::string> SceneSystemComponent::CreateSceneWithParent(
+        AZStd::string_view name, AZStd::shared_ptr<Scene> parent)
+    {
+        const AZStd::shared_ptr<Scene>& existingScene = GetScene(name);
         if (existingScene)
         {
             return AZ::Failure<AZStd::string>("A scene already exists with this name.");
         }
 
-        auto newScene = AZStd::make_unique<Scene>(name);
-        Scene* scenePointer = newScene.get();
-        m_scenes.push_back(AZStd::move(newScene));
-        SceneSystemNotificationBus::Broadcast(&SceneSystemNotificationBus::Events::SceneCreated, *scenePointer);
-        return AZ::Success(scenePointer);
+        auto newScene = AZStd::make_shared<Scene>(name, AZStd::move(parent));
+        m_activeScenes.push_back(newScene);
+        {
+            AZStd::lock_guard lock(m_eventMutex);
+            m_events.Signal(EventType::SceneCreated, newScene);
+        }
+        return AZ::Success(AZStd::move(newScene));
     }
 
-    Scene* SceneSystemComponent::GetScene(AZStd::string_view name)
+    AZStd::shared_ptr<Scene> SceneSystemComponent::GetScene(AZStd::string_view name)
     {
-        auto sceneIterator = AZStd::find_if(m_scenes.begin(), m_scenes.end(),
+        auto sceneIterator = AZStd::find_if(m_activeScenes.begin(), m_activeScenes.end(),
             [name](auto& scene) -> bool
             {
                 return scene->GetName() == name;
             }
         );
 
-        return sceneIterator == m_scenes.end() ? nullptr : sceneIterator->get();
+        return sceneIterator == m_activeScenes.end() ? nullptr : *sceneIterator;
     }
 
-    AZStd::vector<Scene*> SceneSystemComponent::GetAllScenes()
+    void SceneSystemComponent::IterateActiveScenes(const ActiveIterationCallback& callback)
     {
-        AZStd::vector<Scene*> scenes;
-        scenes.resize_no_construct(m_scenes.size());
-
-        for (size_t i = 0; i < m_scenes.size(); ++i)
+        bool keepGoing = true;
+        auto end = m_activeScenes.end();
+        for (auto it = m_activeScenes.begin(); it != end && keepGoing; ++it)
         {
-            scenes.at(i) = m_scenes.at(i).get();
+            keepGoing = callback(*it);
+        }
+    }
+
+    void SceneSystemComponent::IterateZombieScenes(const ZombieIterationCallback& callback)
+    {
+        bool keepGoing = true;
+        auto end = m_zombieScenes.end();
+        for (auto it = m_zombieScenes.begin(); it != end && keepGoing;)
+        {
+            if (!it->expired())
+            {
+                keepGoing = callback(*(it->lock()));
+                ++it;
+            }
+            else
+            {
+                *it = m_zombieScenes.back();
+                m_zombieScenes.pop_back();
+                end = m_zombieScenes.end();
+            }
         }
-        return scenes;
     }
 
     bool SceneSystemComponent::RemoveScene(AZStd::string_view name)
     {
-        for (size_t i = 0; i < m_scenes.size(); ++i)
+        for (AZStd::shared_ptr<Scene>& scene : m_activeScenes)
         {
-            auto& scenePtr = m_scenes.at(i);
-            if (scenePtr->GetName() == name)
+            if (scene->GetName() == name)
             {
-                // Remove any entityContext mappings.
-                Scene* scene = scenePtr.get();
-                for (auto entityContextScenePairIt = m_entityContextToScenes.begin(); entityContextScenePairIt != m_entityContextToScenes.end();)
+                MarkSceneForDestruction(*scene);
                 {
-                    AZStd::pair<EntityContextId, Scene*>& pair = *entityContextScenePairIt;
-                    if (pair.second == scene)
-                    {
-                        // swap and pop back.
-                        *entityContextScenePairIt = m_entityContextToScenes.back();
-                        m_entityContextToScenes.pop_back();
-                    }
-                    else
-                    {
-                        ++entityContextScenePairIt;
-                    }
+                    AZStd::lock_guard lock(m_eventMutex);
+                    m_events.Signal(EventType::ScenePendingRemoval, scene);
                 }
 
-                SceneSystemNotificationBus::Broadcast(&SceneSystemNotificationBus::Events::SceneAboutToBeRemoved, *scene);
-                SceneNotificationBus::Event(scene, &SceneNotificationBus::Events::SceneAboutToBeRemoved);
-
-                m_scenes.erase(&scenePtr);
+                // Zombies are weak pointers that are kept around for situations where there's a delay in deleting the scene. This can happen
+                // if there are outstanding calls like in-progress async calls or resources locked by hardware. A weak_ptr of the original
+                // scene is kept so the zombie scene can still be found through iteration as it may require additional calls such as Tick calls.
+                m_zombieScenes.push_back(scene);
+                scene = AZStd::move(m_activeScenes.back());
+                m_activeScenes.pop_back();
+                // The scene may not be held onto anymore, so check here to see if the previously added zombie can be released.
+                if (m_zombieScenes.back().expired())
+                {
+                    m_zombieScenes.pop_back();
+                }
                 return true;
             }
         }
 
-        AZ_Warning("SceneSystemComponent", false, "Attempting to remove scene name \"%.*s\", but that scene was not found.", static_cast<int>(name.size()), name.data());
+        AZ_Warning("SceneSystemComponent", false, R"(Attempting to remove scene name "%.*s", but that scene was not found.)", AZ_STRING_ARG(name));
         return false;
     }
 
-    bool SceneSystemComponent::SetSceneForEntityContextId(EntityContextId entityContextId, Scene* scene)
+    void SceneSystemComponent::ConnectToEvents(SceneEvent::Handler& handler)
     {
-        Scene* existingSceneForEntityContext = GetSceneFromEntityContextId(entityContextId);
-        if (existingSceneForEntityContext)
-        {
-            // This entity context is already mapped and must be unmapped explictely before it can be changed.
-            char entityContextIdString[EntityContextId::MaxStringBuffer];
-            entityContextId.ToString(entityContextIdString, sizeof(entityContextIdString));
-            AZ_Warning("SceneSystemComponent", false, "Failed to set a scene for entity context %s, scene is already set for that entity context.", entityContextIdString);
-
-            return false;
-        }
-        m_entityContextToScenes.emplace_back(entityContextId, scene);
-        SceneNotificationBus::Event(scene, &SceneNotificationBus::Events::EntityContextMapped, entityContextId);
-        return true;
+        AZStd::lock_guard lock(m_eventMutex);
+        handler.Connect(m_events);
     }
-
-    bool SceneSystemComponent::RemoveSceneForEntityContextId(EntityContextId entityContextId, Scene* scene)
-    {
-        if (!scene || entityContextId.IsNull())
-        {
-            return false;
-        }
-
-        for (auto entityContextScenePairIt = m_entityContextToScenes.begin(); entityContextScenePairIt != m_entityContextToScenes.end();)
-        {
-            AZStd::pair<EntityContextId, Scene*>& pair = *entityContextScenePairIt;
-            if (!(pair.first == entityContextId && pair.second == scene))
-            {
-                ++entityContextScenePairIt;
-            }
-            else
-            {
-                // swap and pop back.
-                *entityContextScenePairIt = m_entityContextToScenes.back();
-                m_entityContextToScenes.pop_back();
-
-                SceneNotificationBus::Event(scene, &SceneNotificationBus::Events::EntityContextUnmapped, entityContextId);
-                return true;
-            }
-        }
-
-        char entityContextIdString[EntityContextId::MaxStringBuffer];
-        entityContextId.ToString(entityContextIdString, sizeof(entityContextIdString));
-        AZ_Warning("SceneSystemComponent", false, "Failed to remove scene \"%.*s\" for entity context %s, entity context is not currently mapped to that scene.", static_cast<int>(scene->GetName().size()), scene->GetName().data(), entityContextIdString);
-        return false;
-    }
-
-    Scene* SceneSystemComponent::GetSceneFromEntityContextId(EntityContextId entityContextId)
-    {
-        for (AZStd::pair<EntityContextId, Scene*>& pair : m_entityContextToScenes)
-        {
-            if (pair.first == entityContextId)
-            {
-                return pair.second;
-            }
-        }
-        return nullptr;
-    }
-
-} // AzFramework
+} // namespace AzFramework

Code/Framework/AzFramework/AzFramework/Scene/SceneSystemComponent.h

@@ -13,18 +13,18 @@
 
 #include <AzCore/Component/Component.h>
 #include <AzCore/std/containers/map.h>
-#include <AzFramework/Scene/SceneSystemBus.h>
+#include <AzCore/std/parallel/mutex.h>
+#include <AzFramework/Scene/SceneSystemInterface.h>
 #include <AzFramework/Entity/EntityContext.h>
 
 namespace AzFramework
 {
     class SceneSystemComponent
         : public AZ::Component
-        , public SceneSystemRequestBus::Handler
+        , public SceneSystemInterface::Registrar
     {
     public:
-
-        AZ_COMPONENT(SceneSystemComponent, "{7AC53AF0-BE1A-437C-BE3E-4D6A998DA945}", AZ::Component);
+        AZ_COMPONENT(SceneSystemComponent, "{7AC53AF0-BE1A-437C-BE3E-4D6A998DA945}", AZ::Component, ISceneSystem);
 
         SceneSystemComponent();
         ~SceneSystemComponent() override;
@@ -41,24 +41,26 @@ namespace AzFramework
         static void GetIncompatibleServices(AZ::ComponentDescriptor::DependencyArrayType& incompatible);
 
         //////////////////////////////////////////////////////////////////////////
-        // SceneSystemRequestsBus::Handler
+        // SceneSystemInterface overrides
         //////////////////////////////////////////////////////////////////////////
-        AZ::Outcome<Scene*, AZStd::string> CreateScene(AZStd::string_view name) override;
-        Scene* GetScene(AZStd::string_view name) override;
-        AZStd::vector<Scene*> GetAllScenes() override;
+        AZ::Outcome<AZStd::shared_ptr<Scene>, AZStd::string> CreateScene(AZStd::string_view name) override;
+        AZ::Outcome<AZStd::shared_ptr<Scene>, AZStd::string> CreateSceneWithParent(
+            AZStd::string_view name, AZStd::shared_ptr<Scene> parent) override;
+        [[nodiscard]] AZStd::shared_ptr<Scene> GetScene(AZStd::string_view name) override;
+        void IterateActiveScenes(const ActiveIterationCallback& callback) override;
+        void IterateZombieScenes(const ZombieIterationCallback& callback) override;
         bool RemoveScene(AZStd::string_view name) override;
-        bool SetSceneForEntityContextId(EntityContextId entityContextId, Scene* scene) override;
-        bool RemoveSceneForEntityContextId(EntityContextId entityContextId, Scene* scene) override;
-        Scene* GetSceneFromEntityContextId(EntityContextId entityContextId) override;
+        void ConnectToEvents(SceneEvent::Handler& handler) override;
 
     private:
+        AZ_DISABLE_COPY_MOVE(SceneSystemComponent);
 
-        AZ_DISABLE_COPY(SceneSystemComponent);
-
-        // Container of scene in order of creation
-        AZStd::vector<AZStd::unique_ptr<Scene>> m_scenes;
-
-        // Map of entity context Ids to scenes. Using a vector because lookups will be common, but the size will be small.
-        AZStd::vector<AZStd::pair<EntityContextId, Scene*>> m_entityContextToScenes;
+        AZStd::vector<AZStd::shared_ptr<Scene>> m_activeScenes;
+        AZStd::vector<AZStd::weak_ptr<Scene>> m_zombieScenes;
+        // Using a mutex around the events as other threads may respond to a new/deleted scene by making
+        // local updates and unregistering themselves. Since Scene is single threaded, no updates (other
+        // then unregistering an event) should be done from other threads though.
+        AZStd::recursive_mutex m_eventMutex;
+        SceneEvent m_events;
     };
 }

Code/Framework/AzFramework/AzFramework/Scene/SceneSystemInterface.h

@@ -0,0 +1,88 @@
+/*
+ * All or portions of this file Copyright (c) Amazon.com, Inc. or its affiliates or
+ * its licensors.
+ *
+ * For complete copyright and license terms please see the LICENSE at the root of this
+ * distribution (the "License"). All use of this software is governed by the License,
+ * or, if provided, by the license below or the license accompanying this file. Do not
+ * remove or modify any license notices. This file is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *
+ */
+#pragma once
+
+#include <AzCore/EBus/EBus.h>
+#include <AzCore/EBus/Event.h>
+#include <AzCore/Interface/Interface.h>
+#include <AzCore/std/smart_ptr/shared_ptr.h>
+#include <AzCore/std/functional.h>
+#include <AzFramework/Entity/EntityContext.h>
+#include <AzFramework/Scene/Scene.h>
+
+namespace AzFramework
+{
+    //! Interface used to create, get, or destroy scenes.
+    //! This interface is single thread and is intended to be called from a single thread, commonly the main thread. The exception
+    //! is connecting events, which is thread safe.
+    class ISceneSystem
+    {
+    public:
+        AZ_RTTI(AzFramework::ISceneSystem, "{DAE482A8-88AE-4BD3-8A5B-52D19A96E15F}");
+        AZ_DISABLE_COPY_MOVE(ISceneSystem);
+
+        enum class EventType
+        {
+            SceneCreated,
+            ScenePendingRemoval
+        };
+        using SceneEvent = AZ::Event<EventType, const AZStd::shared_ptr<Scene>&>;
+
+        ISceneSystem() = default;
+        virtual ~ISceneSystem() = default;
+
+        using ActiveIterationCallback = AZStd::function<bool(const AZStd::shared_ptr<Scene>& scene)>;
+        using ZombieIterationCallback = AZStd::function<bool(Scene& scene)>;
+
+        //! Creates a scene with a given name.
+        //!  - If there is already a scene with the provided name this will return AZ::Failure(). 
+        virtual AZ::Outcome<AZStd::shared_ptr<Scene>, AZStd::string> CreateScene(AZStd::string_view name) = 0;
+
+        //! Creates a scene with a given name and a parent.
+        //!  - If there is already a scene with the provided name this will return AZ::Failure().
+        virtual AZ::Outcome<AZStd::shared_ptr<Scene>, AZStd::string> CreateSceneWithParent(
+            AZStd::string_view name, AZStd::shared_ptr<Scene> parent) = 0;
+
+        //! Gets a scene with a given name
+        //!  - If a scene does not exist with the given name, nullptr is returned.
+        [[nodiscard]] virtual AZStd::shared_ptr<Scene> GetScene(AZStd::string_view name) = 0;
+
+        //! Iterates over all scenes that are in active use. Iteration stops if the callback returns false or all scenes have been listed.
+        virtual void IterateActiveScenes(const ActiveIterationCallback& callback) = 0;
+        //! Iterates over all zombie scenes. Zombie scenes are scenes that have been removed but still have references held on to. This can
+        //! happen because scenes hold on to subsystems that can't immediately be deleted. These subsystems may still require being called
+        //! such as a periodic tick. Iteration stops if the callback returns false or all scenes have been listed.
+        virtual void IterateZombieScenes(const ZombieIterationCallback& callback) = 0;
+
+        //! Remove a scene with a given name and return if the operation was successful.
+        virtual bool RemoveScene(AZStd::string_view name) = 0;
+
+        //! Connects the provided handler to the events that are called after scenes are created or before they get removed.
+        virtual void ConnectToEvents(SceneEvent::Handler& handler) = 0;
+
+    protected:
+        // Strictly a forwarding function to call private functions on the scene.
+        void MarkSceneForDestruction(Scene& scene) { scene.MarkForDestruction(); }
+    };
+
+    using SceneSystemInterface = AZ::Interface<ISceneSystem>;
+
+    // EBus wrapper for ScriptCanvas
+    class ISceneSystemRequests
+        : public AZ::EBusTraits
+    {
+    public:
+        static const AZ::EBusHandlerPolicy HandlerPolicy = AZ::EBusHandlerPolicy::Single;
+        static const AZ::EBusAddressPolicy AddressPolicy = AZ::EBusAddressPolicy::Single;
+    };
+    using ILoggerRequestBus = AZ::EBus<ISceneSystem, ISceneSystemRequests>;
+} // AzFramework

Code/Framework/AzFramework/AzFramework/azframework_files.cmake

@@ -194,10 +194,11 @@ set(FILES
     Logging/MissingAssetLogger.h
     Logging/MissingAssetNotificationBus.h
     Scene/Scene.h
+    Scene/Scene.inl
     Scene/Scene.cpp
-    Scene/SceneSystemBus.h
     Scene/SceneSystemComponent.h
     Scene/SceneSystemComponent.cpp
+    Scene/SceneSystemInterface.h
     Script/ScriptComponent.h
     Script/ScriptComponent.cpp
     Script/ScriptDebugAgentBus.h

Code/Framework/AzToolsFramework/AzToolsFramework/Application/ToolsApplication.cpp

@@ -284,6 +284,10 @@ namespace AzToolsFramework
     void ToolsApplication::Start(const Descriptor& descriptor, const StartupParameters& startupParameters/* = StartupParameters()*/)
     {
         Application::Start(descriptor, startupParameters);
+        if (!m_isStarted)
+        {
+            return;
+        }
 
         m_editorEntityManager.Start();
 

Code/Framework/AzToolsFramework/AzToolsFramework/Entity/EditorEntityContextBus.h

@@ -49,6 +49,8 @@ namespace AzToolsFramework
         /// Retrieve the Id of the editor entity context.
         virtual AzFramework::EntityContextId GetEditorEntityContextId() = 0;
 
+        virtual AzFramework::EntityContext* GetEditorEntityContextInstance() = 0;
+
         /// Creates an entity in the editor context.
         /// \return the EntityId for the created Entity
         virtual AZ::EntityId CreateNewEditorEntity(const char* name) = 0;

Code/Framework/AzToolsFramework/AzToolsFramework/Entity/EditorEntityContextComponent.h

@@ -77,6 +77,7 @@ namespace AzToolsFramework
         //////////////////////////////////////////////////////////////////////////
         // EditorEntityContextRequestBus
         AzFramework::EntityContextId GetEditorEntityContextId() override { return GetContextId(); }
+        AzFramework::EntityContext* GetEditorEntityContextInstance() override { return this; }
         void ResetEditorContext() override;
 
         AZ::EntityId CreateNewEditorEntity(const char* name) override;

Code/Framework/AzToolsFramework/AzToolsFramework/Manipulators/EditorVertexSelection.cpp

@@ -769,12 +769,12 @@ namespace AzToolsFramework
 
     template<typename Vertex>
     void EditorVertexSelectionBase<Vertex>::DisplayViewport2d(
-        const AzFramework::ViewportInfo& /*viewportInfo*/,
+        const AzFramework::ViewportInfo& viewportInfo,
         AzFramework::DebugDisplayRequests& debugDisplay)
     {
         AZ_PROFILE_FUNCTION(AZ::Debug::ProfileCategory::AzToolsFramework);
 
-        m_editorBoxSelect.Display2d(debugDisplay);
+        m_editorBoxSelect.Display2d(viewportInfo, debugDisplay);
     }
 
     template<typename Vertex>

Code/Framework/AzToolsFramework/AzToolsFramework/ToolsComponents/AzToolsFrameworkConfigurationSystemComponent.cpp

@@ -16,7 +16,7 @@
 #include <AzCore/Serialization/EditContext.h>
 
 #include <AzFramework/Scene/Scene.h>
-#include <AzFramework/Scene/SceneSystemBus.h>
+#include <AzFramework/Scene/SceneSystemInterface.h>
 
 #include <AzToolsFramework/Editor/EditorSettingsAPIBus.h>
 #include <AzToolsFramework/Entity/EditorEntityContextComponent.h>
@@ -56,22 +56,47 @@ namespace AzToolsFramework
 
     void AzToolsFrameworkConfigurationSystemComponent::Activate()
     {
-        // Associate the EditorEntityContext with the default scene.
+        // Create the editor specific child scene to the main scene and add the editor entity context to it.
         AzFramework::EntityContextId editorEntityContextId;
         EditorEntityContextRequestBus::BroadcastResult(editorEntityContextId, &EditorEntityContextRequests::GetEditorEntityContextId);
 
-        AzFramework::Scene* defaultScene = nullptr;
-        AzFramework::SceneSystemRequestBus::BroadcastResult(defaultScene, &AzFramework::SceneSystemRequests::GetScene, "default");
-
-        if (!editorEntityContextId.IsNull() && defaultScene)
+        if (!editorEntityContextId.IsNull())
         {
-            bool success = false;
-            AzFramework::SceneSystemRequestBus::BroadcastResult(success, &AzFramework::SceneSystemRequests::SetSceneForEntityContextId, editorEntityContextId, defaultScene);
+            auto sceneSystem = AzFramework::SceneSystemInterface::Get();
+            AZ_Assert(sceneSystem, "Scene system not available to create the editor scene.");
+            AZStd::shared_ptr<AzFramework::Scene> mainScene = sceneSystem->GetScene(AzFramework::Scene::MainSceneName);
+            if (mainScene)
+            {
+                AZ::Outcome<AZStd::shared_ptr<AzFramework::Scene>, AZStd::string> editorScene =
+                    sceneSystem->CreateSceneWithParent(AzFramework::Scene::EditorMainSceneName, mainScene);
+                if (editorScene.IsSuccess())
+                {
+                    AzFramework::EntityContext* editorEntityContext = nullptr;
+                    EditorEntityContextRequestBus::BroadcastResult(
+                        editorEntityContext, &EditorEntityContextRequests::GetEditorEntityContextInstance);
+                    if (editorEntityContext != nullptr)
+                    {
+                        [[maybe_unused]] bool contextAdded =
+                            editorScene.GetValue()->SetSubsystem<AzFramework::EntityContext::SceneStorageType&>(editorEntityContext);
+                        AZ_Assert(contextAdded, "Unable to add editor entity context to scene.");
+                    }
+                }
+                else
+                {
+                    AZ_Assert(false, "Failed to create editor scene because: %s", editorScene.GetError().c_str());
+                }
+            }
+            else
+            {
+                AZ_Assert(false, "No main scene to parent the editor scene under.");
+            }
         }
     }
 
     void AzToolsFrameworkConfigurationSystemComponent::Deactivate()
     {
+        [[maybe_unused]] bool success = AzFramework::SceneSystemInterface::Get()->RemoveScene(AzFramework::Scene::EditorMainSceneName);
+        AZ_Assert(success, "Unable to remove the main editor scene.");
     }
 
     void AzToolsFrameworkConfigurationSystemComponent::GetProvidedServices(AZ::ComponentDescriptor::DependencyArrayType& provided)

Code/Framework/AzToolsFramework/AzToolsFramework/ViewportSelection/EditorBoxSelect.cpp

@@ -13,6 +13,7 @@
 #include "EditorBoxSelect.h"
 
 #include <AzFramework/Entity/EntityDebugDisplayBus.h>
+#include <AzToolsFramework/ViewportSelection/EditorSelectionUtil.h>
 
 #include <QApplication>
 
@@ -72,7 +73,7 @@ namespace AzToolsFramework
         m_previousModifiers = mouseInteraction.m_mouseInteraction.m_keyboardModifiers;
     }
 
-    void EditorBoxSelect::Display2d(AzFramework::DebugDisplayRequests& debugDisplay)
+    void EditorBoxSelect::Display2d(const AzFramework::ViewportInfo& viewportInfo, AzFramework::DebugDisplayRequests& debugDisplay)
     {
         AZ_PROFILE_FUNCTION(AZ::Debug::ProfileCategory::AzToolsFramework);
 
@@ -82,12 +83,15 @@ namespace AzToolsFramework
             debugDisplay.SetLineWidth(s_boxSelectLineWidth);
             debugDisplay.SetColor(s_boxSelectColor);
 
-            debugDisplay.DrawWireBox(
-                AZ::Vector3(
-                    static_cast<float>(m_boxSelectRegion->x()), static_cast<float>(m_boxSelectRegion->y()), 0.0f),
-                AZ::Vector3(
-                    static_cast<float>(m_boxSelectRegion->x()) + static_cast<float>(m_boxSelectRegion->width()),
-                    static_cast<float>(m_boxSelectRegion->y()) + static_cast<float>(m_boxSelectRegion->height()), 0.0f));
+            AZ::Vector2 viewportSize = AzToolsFramework::GetCameraState(viewportInfo.m_viewportId).m_viewportSize;
+
+            debugDisplay.DrawWireQuad2d(
+                AZ::Vector2(
+                    aznumeric_cast<float>(m_boxSelectRegion->x()), aznumeric_cast<float>(m_boxSelectRegion->y())) / viewportSize,
+                AZ::Vector2(
+                    aznumeric_cast<float>(m_boxSelectRegion->x()) + aznumeric_cast<float>(m_boxSelectRegion->width()),
+                    aznumeric_cast<float>(m_boxSelectRegion->y()) + aznumeric_cast<float>(m_boxSelectRegion->height())) / viewportSize,
+                0.f);
 
             debugDisplay.DepthTestOn();
 

Code/Framework/AzToolsFramework/AzToolsFramework/ViewportSelection/EditorBoxSelect.h

@@ -42,7 +42,7 @@ namespace AzToolsFramework
             const ViewportInteraction::MouseInteractionEvent& mouseInteraction);
 
         /// Responsible for drawing the 2d box representing the selection in screen space.
-        void Display2d(AzFramework::DebugDisplayRequests& debugDisplay);
+        void Display2d(const AzFramework::ViewportInfo& viewportInfo, AzFramework::DebugDisplayRequests& debugDisplay);
 
         /// Custom drawing behavior to happen during a box select.
         void DisplayScene(

Code/Framework/AzToolsFramework/AzToolsFramework/ViewportSelection/EditorTransformComponentSelection.cpp

@@ -3494,7 +3494,7 @@ namespace AzToolsFramework
 
         DrawAxisGizmo(viewportInfo, debugDisplay);
 
-        m_boxSelect.Display2d(debugDisplay);
+        m_boxSelect.Display2d(viewportInfo, debugDisplay);
     }
 
     void EditorTransformComponentSelection::RefreshSelectedEntityIds()

Code/Framework/Tests/NetBindingMocks.h

@@ -42,6 +42,7 @@ namespace UnitTest
 
         MOCK_METHOD3(InstantiateDynamicSlice, AzFramework::SliceInstantiationTicket(const AZ::Data::Asset<AZ::Data::AssetData>&, const AZ::Transform&, const AZ::IdUtils::Remapper<AZ::EntityId>::IdMapper&));
         MOCK_METHOD0(GetGameEntityContextId, AzFramework::EntityContextId());
+        MOCK_METHOD0(GetGameEntityContextInstance, AzFramework::EntityContext*());
         MOCK_METHOD1(CreateGameEntity, AZ::Entity*(const char*));
         MOCK_METHOD1(AddGameEntity, void (AZ::Entity*));
         MOCK_METHOD1(DestroyGameEntity, void (const AZ::EntityId&));

Code/Framework/Tests/Scene.cpp

@@ -130,6 +130,8 @@ namespace SceneUnitTest
             m_systemEntity->CreateComponent<AZ::JobManagerComponent>();
             m_systemEntity->CreateComponent<AZ::StreamerComponent>();
             m_systemEntity->Activate();
+
+            m_sceneSystem = AzFramework::SceneSystemInterface::Get();
         }
 
         void TearDown() override
@@ -146,167 +148,119 @@ namespace SceneUnitTest
         AZ::IO::FileIOBase* m_prevFileIO;
         AZ::ComponentApplication m_app;
         AZ::Entity* m_systemEntity = nullptr;
+        AzFramework::ISceneSystem* m_sceneSystem = nullptr;
 
     };
 
     TEST_F(SceneTest, CreateScene)
-    {
-        Scene* scene = nullptr;
-        AZ::Outcome<Scene*, AZStd::string> createSceneOutcome = AZ::Failure<AZStd::string>("");
-
+    {   
         // A scene should be able to be created with a given name.
-        AzFramework::SceneSystemRequestBus::BroadcastResult(createSceneOutcome, &AzFramework::SceneSystemRequestBus::Events::CreateScene, "TestScene");
+        AZ::Outcome<AZStd::shared_ptr<Scene>, AZStd::string> createSceneOutcome = m_sceneSystem->CreateScene("TestScene");
         EXPECT_TRUE(createSceneOutcome.IsSuccess()) << "Unable to create a scene.";
     
         // The scene pointer returned should be valid
-        scene = createSceneOutcome.GetValue();
-        EXPECT_TRUE(scene != nullptr) << "Scene creation reported success, but no scene actually was actually returned.";
+        AZStd::shared_ptr<Scene> scene = createSceneOutcome.TakeValue();
+        EXPECT_NE(scene, nullptr) << "Scene creation reported success, but no scene actually was actually returned.";
 
         // Attempting to create another scene with the same name should fail.
-        createSceneOutcome = AZ::Failure<AZStd::string>("");
-        AzFramework::SceneSystemRequestBus::BroadcastResult(createSceneOutcome, &AzFramework::SceneSystemRequestBus::Events::CreateScene, "TestScene");
+        createSceneOutcome = m_sceneSystem->CreateScene("TestScene");
         EXPECT_TRUE(!createSceneOutcome.IsSuccess()) << "Should not be able to create two scenes with the same name.";
 
     }
 
     TEST_F(SceneTest, GetScene)
     {
-        Scene* createdScene = nullptr;
-        Scene* retrievedScene = nullptr;
-        Scene* nullScene = nullptr;
-        const static AZStd::string_view s_sceneName = "TestScene";
+        constexpr AZStd::string_view sceneName = "TestScene";
 
-        AZ::Outcome<Scene*, AZStd::string> createSceneOutcome = AZ::Failure<AZStd::string>("");
-        AzFramework::SceneSystemRequestBus::BroadcastResult(createSceneOutcome, &AzFramework::SceneSystemRequestBus::Events::CreateScene, s_sceneName);
-        createdScene = createSceneOutcome.GetValue();
+        AZ::Outcome<AZStd::shared_ptr<Scene>, AZStd::string> createSceneOutcome = m_sceneSystem->CreateScene(sceneName);
+        AZStd::shared_ptr<Scene> createdScene = createSceneOutcome.TakeValue();
 
         // Should be able to get a scene by name, and it should match the scene that was created.
-        AzFramework::SceneSystemRequestBus::BroadcastResult(retrievedScene, &AzFramework::SceneSystemRequestBus::Events::GetScene, s_sceneName);
-        EXPECT_TRUE(retrievedScene != nullptr) << "Attempting to get scene by name resulted in nullptr.";
-        EXPECT_TRUE(retrievedScene == createdScene) << "Retrieved scene does not match created scene.";
+        AZStd::shared_ptr<Scene> retrievedScene = m_sceneSystem->GetScene(sceneName);
+        EXPECT_NE(retrievedScene, nullptr) << "Attempting to get scene by name resulted in nullptr.";
+        EXPECT_EQ(retrievedScene, createdScene) << "Retrieved scene does not match created scene.";
 
         // An invalid name should return a null scene.
-        AzFramework::SceneSystemRequestBus::BroadcastResult(nullScene, &AzFramework::SceneSystemRequestBus::Events::GetScene, "non-existant scene");
-        EXPECT_TRUE(nullScene == nullptr) << "Should not be able to retrieve a scene that wasn't created.";
+        AZStd::shared_ptr<Scene> nullScene = m_sceneSystem->GetScene("non-existant scene");
+        EXPECT_EQ(nullScene, nullptr) << "Should not be able to retrieve a scene that wasn't created.";
     }
 
     TEST_F(SceneTest, RemoveScene)
     {
-        Scene* createdScene = nullptr;
-        const static AZStd::string_view s_sceneName = "TestScene";
+        constexpr AZStd::string_view sceneName = "TestScene";
 
-        AZ::Outcome<Scene*, AZStd::string> createSceneOutcome = AZ::Failure<AZStd::string>("");
-        AzFramework::SceneSystemRequestBus::BroadcastResult(createSceneOutcome, &AzFramework::SceneSystemRequestBus::Events::CreateScene, s_sceneName);
-        createdScene = createSceneOutcome.GetValue();
-
-        bool success = false;
-        AzFramework::SceneSystemRequestBus::BroadcastResult(success, &AzFramework::SceneSystemRequestBus::Events::RemoveScene, s_sceneName);
+        AZ::Outcome<AZStd::shared_ptr<Scene>, AZStd::string> createSceneOutcome = m_sceneSystem->CreateScene(sceneName);
+        bool success = m_sceneSystem->RemoveScene(sceneName);
         EXPECT_TRUE(success) << "Failed to remove the scene that was just created.";
 
-        success = true;
-        AzFramework::SceneSystemRequestBus::BroadcastResult(success, &AzFramework::SceneSystemRequestBus::Events::RemoveScene, "non-existant scene");
+        success = m_sceneSystem->RemoveScene("non-existant scene");
         EXPECT_FALSE(success) << "Remove scene returned success for a non-existant scene.";
     }
 
-    TEST_F(SceneTest, GetAllScenes)
+    TEST_F(SceneTest, IterateActiveScenes)
     {
         constexpr size_t NumScenes = 5;
 
-        Scene* scenes[NumScenes] = { nullptr };
+        AZStd::shared_ptr<Scene> scenes[NumScenes] = {nullptr};
 
         for (size_t i = 0; i < NumScenes; ++i)
         {
-            AZ::Outcome<Scene*, AZStd::string> createSceneOutcome = AZ::Failure<AZStd::string>("");
-
             AZStd::string sceneName = AZStd::string::format("scene %zu", i);
-            AzFramework::SceneSystemRequestBus::BroadcastResult(createSceneOutcome, &AzFramework::SceneSystemRequestBus::Events::CreateScene, sceneName);
-            scenes[i] = createSceneOutcome.GetValue();
+            AZ::Outcome<AZStd::shared_ptr<Scene>, AZStd::string> createSceneOutcome = m_sceneSystem->CreateScene(sceneName);
+            scenes[i] = createSceneOutcome.TakeValue();
         }
 
-        AZStd::vector<Scene*> retrievedScenes;
-        AzFramework::SceneSystemRequestBus::BroadcastResult(retrievedScenes, &AzFramework::SceneSystemRequestBus::Events::GetAllScenes);
-
-        EXPECT_EQ(NumScenes, retrievedScenes.size()) << "GetAllScenes() returned a different number of scenes than those created.";
-
-        for (size_t i = 0; i < NumScenes; ++i)
-        {
-            EXPECT_EQ(scenes[i], retrievedScenes.at(i)) << "GetAllScenes() returned scenes in a different order than they were created.";
-        }
+        size_t index = 0;
+        m_sceneSystem->IterateActiveScenes([&index, &scenes](const AZStd::shared_ptr<Scene>& scene)
+            {
+                EXPECT_EQ(scenes[index++], scene);
+                return true;
+            });
     }
 
-    TEST_F(SceneTest, EntityContextSceneMapping)
+    TEST_F(SceneTest, IterateZombieScenes)
     {
-        AZStd::unique_ptr<SliceEntityOwnershipService> m_entityOwnershipService =
-            AZStd::make_unique<AzFramework::SliceEntityOwnershipService>(AZ::Uuid::CreateNull(), m_app.GetSerializeContext());
-        // Create the entity context, entity, and component
-        EntityContext* testEntityContext = new EntityContext(AZ::Uuid::CreateRandom(), AZStd::move(m_entityOwnershipService));
-        testEntityContext->InitContext();
-        EntityContextId testEntityContextId = testEntityContext->GetContextId();
-        AZ::Entity* testEntity = testEntityContext->CreateEntity("TestEntity");
-        TestComponent* testComponent = testEntity->CreateComponent<TestComponent>();
+        constexpr size_t NumScenes = 5;
 
-        // Try to activate an entity and get the scene before a scene has been set. This should fail.
-        TestComponentConfig failConfig;
-        failConfig.m_activateFunction = [](TestComponent* component)
+        AZStd::shared_ptr<Scene> scenes[NumScenes] = {nullptr};
+
+        // Create zombies.
+        for (size_t i = 0; i < NumScenes; ++i)
         {
-            (void)component;
-            Scene* scene = nullptr;
-            EntityContextId entityContextId = EntityContextId::CreateNull();
+            AZStd::string sceneName = AZStd::string::format("scene %zu", i);
+            AZ::Outcome<AZStd::shared_ptr<Scene>, AZStd::string> createSceneOutcome = m_sceneSystem->CreateScene(sceneName);
+            scenes[i] = createSceneOutcome.TakeValue();
+            m_sceneSystem->RemoveScene(sceneName);
+        }
 
-            AzFramework::EntityIdContextQueryBus::BroadcastResult(entityContextId, &AzFramework::EntityIdContextQueryBus::Events::GetOwningContextId);
+        // Check to make sure there are no more active scenes.
+        size_t index = 0;
+        m_sceneSystem->IterateActiveScenes([&index, &scenes](const AZStd::shared_ptr<Scene>&)
+            {
+                index++;
+                return true;
+            });
+        EXPECT_EQ(0, index);
 
-            // A null scene should be returned since a scene has not been set for this entity context.
-            AzFramework::SceneSystemRequestBus::BroadcastResult(scene, &AzFramework::SceneSystemRequestBus::Events::GetSceneFromEntityContextId, entityContextId);
-            EXPECT_TRUE(scene == nullptr) << "Found a scene when one shouldn't exist.";
-        };
-    
-        testComponent->SetConfiguration(failConfig);
-        testComponent->Activate();
-        testComponent->Deactivate();
+        // Check that the scenes are still returned as zombies.
+        index = 0;
+        m_sceneSystem->IterateZombieScenes([&index, &scenes](Scene& scene)
+            {
+                EXPECT_EQ(scenes[index++].get(), &scene);
+                return true;
+            });
 
-        // Create the scene
-        AZ::Outcome<Scene*, AZStd::string> createSceneOutcome = AZ::Failure<AZStd::string>("");
-        AzFramework::SceneSystemRequestBus::BroadcastResult(createSceneOutcome, &AzFramework::SceneSystemRequestBus::Events::CreateScene, "TestScene");
-        Scene* scene = createSceneOutcome.GetValue();
-
-        // Map the Entity context to the scene
-        bool success = false;
-        AzFramework::SceneSystemRequestBus::BroadcastResult(success, &AzFramework::SceneSystemRequestBus::Events::SetSceneForEntityContextId, testEntityContextId, scene);
-        EXPECT_TRUE(success) << "Unable to associate an entity context with a scene.";
-        AzFramework::SceneSystemRequestBus::BroadcastResult(success, &AzFramework::SceneSystemRequestBus::Events::SetSceneForEntityContextId, testEntityContextId, scene);
-        EXPECT_FALSE(success) << "Attempting to map an entity context to a scene that's already mapped, this should not work.";
-
-        // Now it should be possible to get the scene from the entity context within an Entity's Activate()
-        TestComponentConfig successConfig;
-        successConfig.m_activateFunction = [](TestComponent* component)
+        // Check that all scenes are removed when there are no more handles.
+        for (size_t i = 0; i < NumScenes; ++i)
         {
-            (void)component;
-            Scene* scene = nullptr;
-            EntityContextId entityContextId = EntityContextId::CreateNull();
-
-            AzFramework::EntityIdContextQueryBus::BroadcastResult(entityContextId, &AzFramework::EntityIdContextQueryBus::Events::GetOwningContextId);
-
-            // A scene should be returned since a scene has been set for this entity context.
-            AzFramework::SceneSystemRequestBus::BroadcastResult(scene, &AzFramework::SceneSystemRequestBus::Events::GetSceneFromEntityContextId, entityContextId);
-            EXPECT_TRUE(scene != nullptr) << "Could not find a scene for the entity context.";
-        };
-
-        testComponent->SetConfiguration(successConfig);
-        testComponent->Activate();
-        testComponent->Deactivate();
-
-        // Now remove the entity context / scene association and make sure things fail again.
-        success = false;
-        AzFramework::SceneSystemRequestBus::BroadcastResult(success, &AzFramework::SceneSystemRequestBus::Events::RemoveSceneForEntityContextId, testEntityContextId, nullptr);
-        EXPECT_FALSE(success) << "Should not be able to remove an entity context from a scene it's not associated with.";
-        AzFramework::SceneSystemRequestBus::BroadcastResult(success, &AzFramework::SceneSystemRequestBus::Events::RemoveSceneForEntityContextId, testEntityContextId, scene);
-        EXPECT_TRUE(success) << "Was not able to remove an entity context from a scene it's associated with.";
-
-        testComponent->SetConfiguration(failConfig);
-        testComponent->Activate();
-        testComponent->Deactivate();
-
-        delete testEntityContext; // This should also clean up owned entities / components.
+            scenes[i].reset();
+        }
+        index = 0;
+        m_sceneSystem->IterateZombieScenes([&index, &scenes](Scene&) {
+            index++;
+            return true;
+        });
+        EXPECT_EQ(0, index);
     }
 
     // Test classes for use in the SceneSystem test. These can't be defined in the test itself due to some functions created by AZ_RTTI not having a body which breaks VS2015.
@@ -324,30 +278,48 @@ namespace SceneUnitTest
     TEST_F(SceneTest, SceneSystem)
     {
         // Create the scene
-        AZ::Outcome<Scene*, AZStd::string> createSceneOutcome = AZ::Failure<AZStd::string>("");
-        AzFramework::SceneSystemRequestBus::BroadcastResult(createSceneOutcome, &AzFramework::SceneSystemRequestBus::Events::CreateScene, "TestScene");
-        AzFramework::Scene* scene = createSceneOutcome.GetValue();
+        AZ::Outcome<AZStd::shared_ptr<Scene>, AZStd::string> createSceneOutcome = m_sceneSystem->CreateScene("TestScene");
+        EXPECT_TRUE(createSceneOutcome.IsSuccess());
+        AZStd::shared_ptr<Scene> scene = createSceneOutcome.TakeValue();
 
         // Set a class on the Scene
         Foo1* foo1a = new Foo1();
         EXPECT_TRUE(scene->SetSubsystem(foo1a));
 
         // Get that class back from the Scene
-        EXPECT_EQ(foo1a, scene->GetSubsystem<Foo1>());
+        EXPECT_EQ(foo1a, *scene->FindSubsystem<Foo1*>());
 
         // Try to set the same class type twice, this should fail.
         Foo1* foo1b = new Foo1();
         EXPECT_FALSE(scene->SetSubsystem(foo1b));
         delete foo1b;
 
+        // Add a child scene
+        createSceneOutcome = m_sceneSystem->CreateSceneWithParent("ChildScene", scene);
+        EXPECT_TRUE(createSceneOutcome.IsSuccess());
+        AZStd::shared_ptr<Scene> childScene = createSceneOutcome.TakeValue();
+
+        // Get class back from parent scene.
+        EXPECT_EQ(foo1a, *childScene->FindSubsystem<Foo1*>());
+
+        // Find overloaded version of class on child scene.
+        Foo1* foo1c = new Foo1();
+        EXPECT_TRUE(childScene->SetSubsystem(foo1c));
+        EXPECT_EQ(foo1c, *childScene->FindSubsystem<Foo1*>());
+
+        // Unset system on child scene, using alternative unset function.
+        EXPECT_TRUE(childScene->UnsetSubsystem(foo1c));
+        delete foo1c;
+
         // Try to un-set a class that was never set, this should fail.
         EXPECT_FALSE(scene->UnsetSubsystem<Foo2>());
 
         // Unset the class that was previously set
         EXPECT_TRUE(scene->UnsetSubsystem<Foo1>());
+        delete foo1a;
 
-        // Make sure that the previsouly set class was really removed.
-        EXPECT_EQ(nullptr, scene->GetSubsystem<Foo1>());
+        // Make sure that the previously set class was really removed.
+        EXPECT_EQ(nullptr, scene->FindSubsystem<Foo1*>());
     }
 } // UnitTest