121 lines
7.5 KiB
Markdown
121 lines
7.5 KiB
Markdown
# Integration Project
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This is **Luprex**, a game engine built on top of Unreal that uses Lua as its scripting language.
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The system consists of two parts:
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1. The Luprex DLL. Stores the state of the world. Handles networking and lua scripting. The networking is automatic, scripters don't write networking code. The luprex DLL is event-driven, deterministic, OS-independent, no I/O. Pure standard-compliant C++. Organized as a library with struct `EngineWrapper` as the top-level API.
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2. The Unreal-based Driver. Its job is to peer into the luprex DLL and render whatever it sees. It is also responsible for sending OS events (like TCP/IP events) into the Luprex DLL. Uses struct EngineWrapper access the Luprex DLL. There's also a command-line driver for the game's server.
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The luprex DLL never calls into the Unreal driver. Output goes through polled buffers. This separation enables deterministic replay for debugging: the driver logs all events, and can replay them to reproduce crashes.
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## Build System
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- Use `build.py` for all builds. Do NOT follow Epic's standard build instructions.
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- `build.py all` — full rebuild (engine, game, intellisense, project files)
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- `build.py c++` — lightweight rebuild (only if you've only edited C++ files in this repo)
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- Lua and Blueprint edits don't require a rebuild.
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## Directory Structure
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- `luprex/` — The Luprex DLL.
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- `Source/Integration/` — Game module C++ source (Unreal-side driver code)
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- `Content/` — Unreal assets
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- `Docs/` — Documentation. When trying to understand this system, start with the markdown files in the Docs directory.
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- `Config/` — Unreal config files
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- `EnginePatches/` — Custom engine modifications
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## Architecture: World Models and Predictive Reexecution
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There are four types of world models, each a separate `World` instance with its own Lua interpreter:
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- **Master** (server, one) — authoritative state, executes commands immediately when they arrive.
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- **Server-synchronous** (server, one per client) — executes commands when the acknowledgement is issued.
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- **Client-synchronous** (client, one) — executes commands when the same acknowledgement arrives; determinism keeps it in perfect sync with its server-synchronous counterpart.
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- **Asynchronous** (client, one) — snapshot of client-synchronous with predictions applied for responsive rendering; rolled back when server confirms.
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The synchronous models lag behind the master but stay in lockstep with each other. The asynchronous model fills the latency gap for the player.
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Two update channels flow into the synchronous models:
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1. **Command acknowledgements** — for the client's own actions, keeping the two synchronous models in lockstep.
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2. **Difference transmission** — for everything else (other players' actions, server-side events, tangibles entering/leaving visibility).
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See `Docs/Predictive-Reexecution.md` for the full explanation.
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## Architecture: Lua / Unreal Separation
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Lua scripts have no access to the Unreal API whatsoever. The scripter works with plain Lua tables, animation queues of key-value tuples, and coroutines. There are no "unreal bindings." The Luprex DLL is engine-agnostic — Unreal (or any other front end) interprets the animation queues and renders accordingly.
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Small concessions to reality exist in animation step tuples:
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- `bp` — names which Tangible Actor blueprint to use for rendering
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- `mat_color` — a persistent value that hints at material color
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These are still just key-value data; the script never touches the Unreal API directly.
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## Architecture: Tangibles
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Tangibles are game objects. Each has:
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- A **Lua table** — the scripter stores arbitrary game data here.
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- An **animation queue** — a fixed-length sequence of key-value animation steps.
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- A **C++ tangible** — holds the ID, animation queue, positional tracker, etc.
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- A **metatable** — engine-reserved; contains __id, __index (class), __threads.
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Animation steps contain **transient** values (like `action`) that don't propagate, and **persistent** values (like `xyz`, `facing`, `plane`) that carry forward automatically.
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On the Unreal side, **Tangible Actor blueprints** (TangibleStaticMesh, TangibleSkeletalMesh, TangibleCharacter) monitor the animation queue and perform the visual animations. Custom blueprints can interpret the queue in any way they want.
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## Architecture: Lua Environment
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- **Patched Lua runtime** — deterministic table iteration, deterministic table length, flag bits on tables, generalized less-than, C++ exceptions instead of longjmp, and more. See `Docs/A-Summary-of-our-Lua-Patches.md`.
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- **LuaStack API** — custom C++ API replacing the standard Lua C API. Uses `LuaDefStack`/`LuaExtStack` with `LuaArg`/`LuaVar`/`LuaRet` slots mapped to stack positions. See `Docs/Our-In-House-Lua-API.md`.
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- **LuaDefine macro** — declares Lua-callable C++ functions and auto-registers them in a global registry for automatic insertion into the Lua environment.
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- **eng::malloc heap** — custom deterministic memory allocator for the driven portion, ensuring reproducible addresses during replay.
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## Architecture: Determinism
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The driven portion must be fully deterministic so that synchronous models stay in lockstep and event replay works. Rules: no true random numbers, no iterating unordered maps, no real-time clocks, no threads (with carefully sandboxed exceptions). See `Docs/The-Event-Driven-Structure-of-the-Engine.md`.
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## Architecture: GUI System
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Blueprints call into Lua via two mechanisms:
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- **Invokes** — change world state, forwarded to server, executed in order per predictive reexecution rules.
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- **Probes** — read-only, return data to blueprints, run locally on client.
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Look-at widgets, hotkeys, and menus are built on top of this. The menu system is implemented entirely in "user space" Lua and blueprint code. See `Docs/Displaying-Widget-Blueprints.md`.
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## Blueprint Text Export
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Blueprints are automatically exported to readable text files in `Saved/BlueprintExports/` whenever they are saved in the editor. This lets Claude Code read blueprint logic. See `Docs/Blueprint Text Export.md` for format details. Source: `Source/Integration/BlueprintExporter.h/.cpp` and `Source/Integration/Integration.cpp`.
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## Key Documentation
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Look in the Docs directory for important documentation.
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## Git
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Do not use git to make changes (commit, push, branch, etc.). Read-only git commands (status, log, diff, etc.) are fine.
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## Workflow
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- When the user gives a direct command, execute it. But when proposing changes on your own initiative, describe the plan and get approval before editing files.
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- If an instruction ends with an ellipsis (`...`), the user has more to say. Wait for the next message before acting.
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## Coding Conventions
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- Prefer early returns and `continue` to reduce nesting (never-nester style).
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- Do not use static functions in Unreal code. Use class methods or namespace-scoped functions instead.
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- Use `LogLuprexIntegration` for log messages, not `LogTemp`.
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- When writing UFUNCTIONs that take an `AActor*`, `UObject*`, or similar "self" parameter, add `DefaultToSelf` meta to that pin. Most functions should have this on the obvious pin so the user doesn't have to manually wire it in blueprints.
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## Session Startup
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At the beginning of every session, do a directory listing of these three directories so you know what files are available:
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- `Docs/` — documentation
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- `Source/Integration/` — Unreal-side C++ code
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- `luprex/cpp/core/` — Luprex DLL core C++ code
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These two code directories contain 99% of the code we'll be working on together.
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## Current Status
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(Use this section to track what we're working on across sessions.)
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