vozdyxstuff/re-ue4ss

Purpose and Deliverables

UE4SS is a native Unreal Engine 4/5 runtime extension for game modding, inspection, and reverse-engineering. It is deployed into a game’s Win64 binaries directory, typically through a proxy DLL, then exposes Lua and C++ mod APIs, Blueprint loading, reflection/property tooling, and code/mapping generators. Primary runtime sources are UE4SS/src/main_ue4ss_rewritten.cpp, UE4SS/src/UE4SSProgram.cpp, and UE4SS/src/UE4SSRuntime.cpp.

Injection and Runtime Bootstrap

A generated proxy DLL forwards a chosen Windows DLL’s exports while loading UE4SS into the game process. UE4SS/proxy_generator/main.cpp and UE4SS/proxy_generator/proxy/CMakeLists.txt define this proxy-generation/deployment boundary. The core program initializes crash handling, settings, signature resolution, hooks, and the runtime against the host Unreal process (UE4SS/src/UE4SSProgram.cpp, UE4SS/src/UE4SSRuntime.cpp, UE4SS/src/Signatures.cpp).

Unreal Compatibility and Memory Boundary

UE4SS bridges into an unknown game/engine binary through AOB signatures, version-specific layouts, and direct Unreal object access. UE4SS/include/UnrealDef.hpp supplies engine-facing definitions; UE4SS/include/Signatures.hpp represents address discovery; UE4SS/include/UnrealCustom/CustomProperty.hpp supports nonstandard reflected properties. Per-game overrides—settings, signatures, member-variable, and vtable layouts—are distributed under assets/CustomGameConfigs/; e.g., assets/CustomGameConfigs/Satisfactory/UE4SS-settings.ini.

Mod Execution Model

The mod layer supports Lua scripts and native C++ DLL mods through a shared mod abstraction: UE4SS/include/Mod/Mod.hpp, UE4SS/src/Mod/LuaMod.cpp, and UE4SS/src/Mod/CppMod.cpp. Runtime discovery/configuration loads bundled and user mod directories, with Lua scripts such as assets/Mods/BPModLoaderMod/Scripts/main.lua using the exposed API. The Lua boundary consists of interpreter/library setup and bindings for Unreal types, containers, hooks, scheduling, and custom properties (UE4SS/src/LuaLibrary.cpp, UE4SS/src/LuaType/LuaUObject.cpp, UE4SS/include/LuaCustomMemberFunctions.hpp).

UI, Inspection, and Diagnostics

An in-process ImGui UI provides console, debugger, profiler, dump controls, and live object/property viewing. The UI coordinator is UE4SS/src/GUI/GUI.cpp; rendering backends include DirectX 11 and GLFW/OpenGL (UE4SS/src/GUI/DX11.cpp, UE4SS/src/GUI/GLFW3_OpenGL3.cpp). Live View reads and edits loaded Unreal objects through reflection filters (UE4SS/src/GUI/LiveView.cpp, UE4SS/include/GUI/LiveView/Filter/HasProperty.hpp). Filesystem watching allows runtime reaction to asset/mod changes (UE4SS/src/FilesystemWatcher.cpp).

Generation and Dump Pipelines

Runtime reflection data can be converted into SDK headers, UHT-compatible headers, JSON, object text, and .usmap mappings. SDK generation is centered on UE4SS/src/SDKGenerator/Generator.cpp and UE4SS/src/SDKGenerator/UEHeaderGenerator.cpp; mapping generation is in UE4SS/src/USMapGenerator/Generator.cpp. These output-oriented stages are separated from the injected mod runtime but consume its discovered Unreal metadata.

Companion Tool and Build Infrastructure

UVTD is a separate native command-line tool for PDB/symbol analysis and generating Unreal virtual/member-variable/Lua-binding artifacts (UVTD/src/main.cpp, UVTD/src/UVTD.cpp, UVTD/src/UnrealVirtualGenerator.cpp). The repository is principally C++23/CMake, with xmake metadata and a Rust patternsleuth_bind dependency (CMakeLists.txt, UE4SS/CMakeLists.txt, deps/first/patternsleuth_bind/src/lib.rs). Material dependencies include Lua, PolyHook, Zydis, ImGui, GLFW, OpenGL/GLAD, Tracy, raw PDB parsing, and the Unreal pseudo-code submodule. Windows is the deployment target; Linux is supported for Windows cross-compilation via xwin or Wine/MSVC toolchains.