arcattackandClaude Opus 4.8
f52bf057e6
The byte-exact WORLD-ENTITY reconstruction (Projectile @4be1bc 0x340 / Missile @4bf5b4 0x368)
is infeasible on the 2007 engine: measured sizeof(engine Entity)=0x1BC vs the 1995 binary's
0x300, so the reconstruction's raw base-offset reads (velocity@0x1dc, roster@0x124, motion@0x250)
read GARBAGE on the engine (the Mech 0x638-vs-0x854 gap, but the entity integrator DEPENDS on
those offsets). So -- like the mech drive and the beam renderer -- flying projectiles are a PORT
reconstruction (BTPushProjectile/BTUpdateProjectiles in mech4.cpp, a static array + stack
messages, ZERO heap ops): seeded from the launcher's fire with the decomp's real muzzle
(GetMuzzlePoint) / launch speed (|launchVelocity|) / per-shot damage (damageData, split across
missileCount), they fly to the target (tracer via BTPushBeam) and deliver the weapon's damage on
impact through the SAME Entity::TakeDamage path as the beam (aim Mech::FirstVitalZone()).
THREE bring-up fixes were needed to make a projectile weapon fire at all (found by tracing):
1. TRIGGER: fireImpulse was only driven for the Emitter; ProjectileWeaponSimulation now sets
fireImpulse = gBTWeaponTrigger too (else CheckFireEdge never sees an edge).
2. AMMO BIN: OwnerSubsystemCount/OwnerSubsystem were stubbed ->0, so ammoBinLink never resolved
and ConsumeRound always failed; redirected to the real roster (owner->GetSubsystemCount()/
GetSubsystem(i) -- the AmmoBin 0xBCB constructs before the weapons 0xBCD/0xBD0).
3. JAM ROLL: UniformRandom() was stubbed `return 0.0f`, so CheckForJam's `0 < jamChance` ALWAYS
jammed (a projectile weapon could NEVER fire); replaced with a real LCG [0,1) (fires
~1-jamChance of the time -- authentic occasional jams).
Also: the mech's own target slot (owner+0x388) isn't populated in bring-up (the visible fire
targets the gEnemyMech global), so BTPushProjectile falls back to gEnemyMech.
Verified: Mad Cat PUSH=62 / IMPACT=31 (LRM missiles 3.33 dmg each split across the salvo + AFC100
autocannon 25 dmg), TARGET DESTROYED, 0 crashes, construction heapcheck-clean; BLH un-regressed
(also fires its ballistic weapon now). Diagnostics BT_PROJ_LOG ([projectile] PUSH/IMPACT).
REMAINING (deferred): the byte-exact world-entity Missile (Projectile : Mover, MP-replicable via
Registry::MakeEntity) -- the port projectile is master-local only (no MP replication); the real
per-weapon fire-rate/heat wiring off the subsystem sim (mech4 beam path is still the bring-up harness).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
BattleTech 4.11 (bt411)
A standalone Windows port of Virtual World Entertainment's arcade BattleTech (Tesla platform, release 4.10, ~1995–96), reconstructed on the shared RP411 Windows engine. The game boots, renders, and runs a single-player drive → animate → target → fire → damage → destroy loop across all 8 maps, with two-instance multiplayer entity replication working.
This repo is a clean, self-contained extraction of the BattleTech-specific work from the larger reverse-engineering workspace — engine + game + content + build, with nothing from Red Planet or the raw archive dumps. It builds and runs out of the box.
License: the game content (
content/) and the original binary are proprietary to Virtual World / the pod owner. This repository is private; do not redistribute.
Layout
CMakeLists.txt one build: munga_engine lib + bt410_l4 game lib + btl4.exe
engine/
MUNGA/ shared 2007 sim/render engine (149 .cpp + headers)
MUNGA_L4/ Win32/D3D9 HAL + renderer + asset loaders (43 .cpp), incl.
our BT work: bgfload / L4D3D / L4VIDEO + the image codec
shim/ minimal ATL shim (USES_CONVERSION/W2A)
lib/ OpenAL32 / libsndfile import libs + runtime DLLs
game/
reconstructed/ the reconstructed BT game logic (mech, subsystems, HUD, app)
original/BT,BT_L4 surviving original BT source + all BT headers
fwd/ header shims forwarding <NAME.hpp> -> the engine's NAME.h
btl4main.cpp WinMain launcher / entry point
content/ runtime data: BTL4.RES, VIDEO/, GAUGE/, AUDIO/, *.EGG, BTDPL.INI
docs/ format specs (BGF, assets) + reconstruction ledgers
reference/
decomp/ raw Ghidra pseudocode — source-of-truth for ongoing recon
ghidra_scripts/ the headless decomp exporter
tools/ btconsole.py (MP console emulator), map/resource scanners
run/ run.cmd helper
CLAUDE.md full project context / progressive knowledge base
Prerequisites
- Visual Studio 2019 BuildTools (MSVC v142, x86). The Community install on the original dev box was broken, hence the explicit BuildTools instance in the configure line below; adjust to your install.
- CMake ≥ 3.20.
- Legacy DirectX SDK (June 2010) — the engine uses
d3dx9/dinput/dxerr, removed from the modern Windows SDK. Default pathC:/Program Files (x86)/Microsoft DirectX SDK (June 2010); override with-DDXSDK=<path>. (The installer may throw a harmless S1023 error — dismiss it; the SDK headers/libs install before the failing redist step.)
OpenAL/libsndfile import libs + DLLs are vendored under engine/lib/; the DLLs are copied next to
the exe automatically at build time.
Build (32-bit / Win32)
cmake -S . -B build -G "Visual Studio 16 2019" -A Win32 ^
-DCMAKE_GENERATOR_INSTANCE="C:/Program Files (x86)/Microsoft Visual Studio/2019/BuildTools"
cmake --build build --config Debug
Must be Win32 — the DirectX SDK link libs are Lib/x86. The link uses /FORCE: the 1995
headers define free functions/globals without inline/extern, so identical symbols appear in
many translation units (~124 LNK2005); /FORCE:MULTIPLE keeps the first. UNRESOLVED tolerates
a dead offline-tool factory in mech3.cpp that is never called at runtime. (Cleanup task: move
those definitions to single TUs + neutralize the dead factory, then drop /FORCE.)
Run
run\run.cmd REM boots DEV.EGG (grass / day)
run\run.cmd DBASE.EGG REM any egg in content/
The working directory must be content/ (the engine resolves BTL4.RES, VIDEO\,
BTDPL.INI, and eggs relative to cwd); run.cmd handles that. Maps available in BTL4.RES:
cavern grass rav polar3 polar4 arena1 arena2 dbase — switch via a copied egg's map= field.
Useful env-var flags (default OFF unless noted)
The authentic stack (gait, collision, real controls) is default-on; set =0 to fall back.
Debug/harness flags: BT_FORCE_THROTTLE=1 (auto-walk), BT_SPAWN_ENEMY=1 (spawn a target dummy),
BT_FORCE_FIRE=1 (auto-fire), BT_HEAPCHECK=1 (whole-heap validation — slow), BT_BSL=0 (legacy
texture decode), BT_LOG=<file>. Interactive: WASD drive, Space/Ctrl fire, X all-stop.
See CLAUDE.md for the complete list and the reconstruction history.
Multiplayer (two instances, one box)
instance A: btl4.exe -egg MP.EGG -net 1501 (BT_LOG=mp_a.log)
instance B: btl4.exe -net 1601 (BT_LOG=mp_b.log)
console: python tools/btconsole.py MP.EGG 127.0.0.1:1501 127.0.0.1:1601
-net <port> enables networked mode; the console emulator delivers the mission egg and the launch
command. Entity + movement replication works; cross-pod combat is in progress.
Status & continuing the work
The engine, renderer, audio, HAL, build, locomotion, collision, damage, and render fidelity are
done; per-subsystem reconstruction (gyro integrator, projectile/missile weapons) and MP combat are
the active fronts. docs/ holds the format specs and reconstruction ledgers; reference/decomp/
holds the raw pseudocode that every reconstruction is verified against. CLAUDE.md is the durable,
progressive project context — read it first.