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`make bench` is one recipe over one run now. `IW4L_BENCH=1` arms an in-process recorder on the spans that already feed Perfetto, and at exit the run prints two independent reports and writes them to `iw4l-artifacts/bench/<stamp>.txt`: the waterfall from the shell command to a playable map, carrying the time each load stage held the pool alone, and frame time as a span tree whose nesting is recorded rather than declared. Neither needs a trace file or Trace Processor, and either can be MISS while the other stands. `bench-demo` and `bench-load` are gone — a goal after `bench` is a demo, `ZONE=` is a live map. A bot is no longer minted onto an id a real client already owns. The roster steps over the ids the authority and the local player hold, and a slot that still lands on the local player is retired, because `is_bot` would otherwise claim the player and nothing could drive the slot anyway. A stretch with no authority ack re-adopts the next snapshot and counts one stall; three of them still fail the link. Failing on the first turned every long frame into a permanent disconnect. The loading overlay comes down once the world is installed rather than waiting on the class-select hop, which a replay never makes — it was playing the whole demo behind `UiLayer::Loading`, with map ambience held back. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_013bHwyKwUjaYmtVG1F3Ttku
IW4L
IW4L is a Call of Duty runtime written from scratch in Rust, on bevy and wgpu. Point it at a copy of MW2 you already own and it loads that install's data into its own engine.
The on-disk layouts came out of reverse engineering the original binaries and reading public technical references.
This whole project is written by an LLM.
Status
No releases yet: you build it from this tree. Nothing here is stable either — the API, the config format, caches and the wire protocol all change between commits, so everyone in a session needs to be on the same one. Expect bugs and desyncs.
The network side is for arranged playtests among people who already agreed to play; it has never been vetted for lobbies full of strangers. IW4L sends nothing home, and diagnostic files sit on your disk until you attach them to a report.
Architecture
| assets | MW2 zones read natively; MW3 and Black Ops land in the same asset_iw4 IR. |
| shaders | Retail D3D9 SM3 tokens translated to WGSL, so no DirectX at runtime. |
| rendering | One sorted drawsurf list; only the tess emitters fork per surface type. |
| physics | Fixed 17 ms step on its own accumulator. Framerate changes nothing about how a body falls. |
| simulation | One TickInput → sim::step → Snapshot funnel for server, prediction, replay and the determinism test. |
| network | Custom p2p wire over UDP: deltas, reliability, reconciliation. A QUIC master only introduces peers. |
| platforms | Linux and a portable Windows build. |
Retail protocols, the original ABI and patched executables are out of scope. IW4L clients talk to IW4L clients.
Game data
IW4L_GAMES points at the folder holding your game trees. No assets ship in
this repository or in any release, and IW4L is unaffiliated with the rights
holders of the original games.
Those trees are read only. IW4L never patches them, swaps files in them or
writes anything back; caches, settings, demos and logs land in
iw4l-artifacts/ next to the IW4L binary.
Build and run
cp .env.example .env # IW4L_GAMES — folder containing the game trees
make map mp_boneyard # run a map
make map mp_boneyard CMDS='spawn assault; wait 2s; quit'
make help # every recipe
Live runs use [profile.play], a development build with optimizations turned
on. PROFILE=release builds the real release binary.
docs/WINDOWS.md covers Windows.
Documentation
Implementation notes live under docs/, one short file per area. Start at
docs/INDEX.md.
| file | about |
|---|---|
docs/RUN.md |
running the game, console scripts, commands and traps |
docs/PERF.md |
Perfetto tracing and performance analysis |
docs/RENDER.md |
rendering pipeline |
docs/MAP-LOAD.md |
map loading and asset installation |
docs/ENTITIES.md |
simulation data flow and entity taxonomy |
docs/SIM-STEP.md |
simulation step architecture |
docs/ANIM.md |
animation system |
docs/WINDOWS.md |
portable Windows build |
docs/DEPLOY.md |
release, publishing and deployment |
docs/MASTER.md |
running your own master server |
Contributing and support
A personal, experimental project. Bug reports are welcome and get no promised
fix date. CONTRIBUTING.md says what a useful report
contains and how changes get reviewed; security reports go to
SECURITY.md.
Acknowledgements
IW4L ships none of the code below. It was read against all of it.
- OpenAssetTools and its iw4x-x64 fork — modding tools whose asset-structure headers document the on-disk layouts IW4L reads.
- IW4x — a custom client for MW2 (2009), a cross-reference for asset and protocol behaviour.
- KisakCOD — an open-source CoD4 reimplementation, a cross-reference for engine structure one generation over in the same family.
- Ghidra — the framework the original binaries were read with.
License
IW4L is licensed under the Apache License 2.0, and
NOTICE holds the copyright notices, the licences of the projects
above and the bundled fonts. That licence covers IW4L's own source code. Call
of Duty, Modern Warfare, Black Ops and the related assets, trademarks and
intellectual property belong to their respective owners.