When working with Unreal Engine 5 (UE5) source code, understanding how different layers and modules map to the actual file structure is crucial. Below is a detailed mapping that shows where you can find the relevant code in the UE5 source code directory.

🔍 UE5 Source Code Structure Overview

UE5 source code is structured in the following way:

📁 Engine/Source/ → The root folder for Unreal Engine source code.
📁 Engine/Plugins/ → Contains optional modules and platform-specific extensions.
📁 Engine/Config/ → Configuration files for different engine components.

Each module has a dedicated folder inside Engine/Source/, typically following this structure:

📁 ModuleName/
├ 📄 ModuleName.Build.cs → Build rules for the module.
├ 📄 ModuleName.h → Main header file defining the module.
├ 📄 ModuleName.cpp → Main implementation file.
├ 📁 Private/ → Internal implementation files.
├ 📁 Public/ → Public headers for other modules to use.

📌 Layer, Module, and Source Code Folder Mapping

The following table shows where to find each module in the UE5 source code.

Layer Module Source Code Location Key Files to Look At
Game Layer Game Code (C++, Blueprints) 📁 YourGame/Source/YourGame/ YourGameGameMode.cpp (Game Mode logic), YourGameCharacter.cpp (Player logic)
  Asset Management (Pak, Virtual Texturing) 📁 Engine/Source/Runtime/Engine/ TextureStreamingManager.cpp, AssetManager.cpp
Framework Layer Gameplay Framework (Actors, GameMode, Pawns) 📁 Engine/Source/Runtime/Engine/ GameModeBase.cpp, AActor.cpp, UWorld.cpp
  AI System (NavMesh, Behavior Trees) 📁 Engine/Source/Runtime/AIModule/ NavigationSystem.cpp, BehaviorTreeComponent.cpp
  Input System (Enhanced Input, Touch) 📁 Engine/Source/Runtime/InputCore/ EnhancedInputComponent.cpp, TouchInterface.cpp
  UI System (Slate, UMG, Common UI) 📁 Engine/Source/Runtime/Slate/
📁 Engine/Source/Runtime/UMG/		 SlateApplication.cpp, UserWidget.cpp
Engine Layer Engine (World, Actors, Input, Events) 📁 Engine/Source/Runtime/Engine/ GameInstance.cpp, LevelStreaming.cpp
  RenderCore (Rendering Pipeline) 📁 Engine/Source/Runtime/RenderCore/ Renderer.cpp, RenderGraph.cpp
  RHI (Render Hardware Interface) 📁 Engine/Source/Runtime/RHI/ RHI.cpp, DynamicRHI.cpp
  PhysicsCore (Chaos Physics Engine) 📁 Engine/Source/Runtime/PhysicsCore/ PhysicsEngine.cpp, ChaosSolver.cpp
  Audio (SoundCore, AudioMixer) 📁 Engine/Source/Runtime/AudioMixer/ AudioMixer.cpp, DSP.cpp
  Networking (NetDriver, Replication) 📁 Engine/Source/Runtime/Online/ NetDriver.cpp, ReplicationGraph.cpp
Core Layer Core (Memory, Logging, Math, Threading) 📁 Engine/Source/Runtime/Core/ Core.cpp, ThreadManager.cpp
  CoreUObject (Serialization, GC) 📁 Engine/Source/Runtime/CoreUObject/ UObjectBase.cpp, GarbageCollection.cpp

🔎 How to Find & Modify Modules in Source Code

  1. Locate the Module Folder
    • Go to Engine/Source/Runtime/ for core engine modules.
    • Go to YourGame/Source/ for game-specific modules.
    • Use Visual Studio’s Solution Explorer to browse files.
  2. Find the Build Script (.Build.cs)
    • Every module has a ModuleName.Build.cs file.
    • This file defines dependencies and compilation settings.
  3. Modify the Relevant .cpp and .h Files
    • Gameplay: Modify AActor.cpp, GameModeBase.cpp, or AIController.cpp.
    • Rendering: Edit RenderCore.cpp or RHI.cpp.
    • Physics: Optimize ChaosSolver.cpp.
    • Networking: Adjust replication settings in NetDriver.cpp.
  4. Recompile & Test
    • Run GenerateProjectFiles.bat (Windows) or GenerateProjectFiles.sh (Mac/Linux).
    • Open Visual Studio and build the engine/game.
    • Use Unreal Insights to measure performance after changes.

🚀 Best Practices for Mobile Porting

✔ Disable Unused Modules

  • Modify YourGame.Target.cs to remove unnecessary desktop features.
    ✔ Optimize Rendering (RenderCore, RHI)
  • Switch to Mobile Forward Rendering.
  • Disable Nanite & Lumen.
    ✔ Reduce Physics Overhead (PhysicsCore)
  • Use simple collision meshes.
    ✔ Improve AI Efficiency (AIModule)
  • Lower AI tick rate and avoid expensive NavMesh updates.

📌 Final Takeaway

  • Engine source is modular → Find code inside Engine/Source/Runtime/.
  • Each module has a Build.cs file → Modify dependencies there.
  • Use this mapping to navigate quickly → Find relevant files for optimization and mobile adjustments.

Need help tweaking a specific module? Let me know! 🚀