BT411/docs/BT_SOURCE_STATUS.md

BattleTech (Tesla 4 / rel 4.10) — Source Status & Reconstruction

Purpose: brief for a meeting with an original BT programmer. What source we have, what was missing, where each piece came from, and how we're patching the gaps to get BT running on modern Windows. The most useful thing you can tell us is at the bottom (§7).

One-line status: the port now compiles, links, and boots to a window, and is running into the mission/spawn simulation. The engine/renderer/audio came from an existing Windows port (Red Planet); the BT game logic was lost and is being reconstructed from the shipped binary + the surviving headers + Red Planet's parallel code.

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1. The situation in one picture

Layer	Have it?	Source
MUNGA engine + L4 HAL (renderer, mover, math, scene, net, audio)	✅ complete	The Windows port ("WinTesla", Red Planet 4.11 source) — already bypasses the Division IG board with Direct3D 9 (L4D3D) and replaces HMI SOS audio with OpenAL.
BT headers (.hpp: class layouts, vtables, signatures)	⚠️ partial	~14 survived in the BT source archive (410srczipped); the core ~28 (mech, heat, powersub, weapons, btplayer, hud, gauges…) were lost — see §3.
BT game logic (mech, subsystems, weapons, HUD, app…) .cpp	❌ LOST	Reconstructed from the shipped binary BTL4OPT.EXE (decompiled).
Deployed content (models, skeletons, skins, animations, missions/eggs)	✅ present	The pod machine disk image.

Where a header survived it's an answer key for class layout/vtable order (then the binary just supplies the bodies). Where it didn't (the core mech/weapon/player classes), the layout itself is inferred from the binary's vtables + this+offset usage, cross-checked against the Red Planet analog — a harder reconstruction, and the part most worth validating against original source if any exists.

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2. Where everything lives (the four archives, in the repo root)

Archive	What it is	Key contents
410srczipped.zip	BT source tree	All .hpp headers, geometry/material defs, 428 animations, and a partial set of .cpp. Build manifests CODE/BT/BT/BT.MAK + CODE/BT/BT_L4/BTL4.MAK (the authoritative file lists).
Tesla4NovellTechPC-*.zip	Pod technician/test PC image	The compiled game btrel410.exe, Division VPX board diagnostics, shared textures.
Tesla4PodPCNovell-*.zip	The pod game machine image	The full deployed content tree at …/CopyofNovellDisk/REL410/BT/ — per-mech skeletons/skins, models, textures, gauges, and the mission eggs (TEST.EGG, LAST.EGG). Also a copy of the game binary.
Elsewhen RP411 Source-*.zip	The Windows port ("WinTesla", VS2008)	Modernized engine: WinTesla.sln, MUNGA + MUNGA_L4 (incl. L4D3D.cpp = IG→Direct3D), OpenAL/libsndfile audio, and the complete Red Planet game logic. The solution references a BT410_L4 target but the BT game source folder is absent — confirming BT was mid-port and its code isn't here.

The shipped binary btrel410.exe is a PKZIP self-extractor; unwrapped it yields BTL4OPT.EXE (1.24 MB, clean PE32) — that's our decompilation + behavioral oracle.

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3. What was missing, precisely (from BT.MAK + BTL4.MAK = 53 modules)

Every module in the original build manifests is accounted for as follows:

3a. Survived as real source (~10) — used as-is

From CODE/BT/BT/ and CODE/BT/BT_L4/: BTMSSN (mission), BTREG (registry), BTTEAM, BTSCNRL (scenario role), BTCNSL (console), BTTOOL, GAUSS (Gauss rifle), PPC, BTL4ARND (arena), BTL4MODE (mode manager).

3b. Lost → reconstructed from the binary (~43 modules)

The heart of the game. Two cases, depending on whether the header also survived:

(i) Header AND .cpp lost → both reconstructed (class layout/vtable inferred from the binary + RP analog — these are the ones whose layout is our inference, not ground truth): mech, mech2, mech3, mech4, mechsub, dmgtable, heat, heatfamily_reslice, powersub, gnrator, gyro, torso, myomers, searchlight, thermalsight, mechweap, emitter, projweap, missile, projtile, ammobin, btplayer, mechmppr, btl4vid, btl4mppr, hud, btl4gaug, btl4gau2, btl4gau3.

(ii) .hpp survived, only .cpp lost → implementation reconstructed against the real header (lower risk — layout is ground truth): mechdmg, mechtech, sensor, messmgr, mislanch, misthrst, seeker, btl4app, btl4mssn, btl4rdr, btl4grnd, btl4pb, btl4galm, btdirect.

(Surviving headers with no reconstruction needed — interface-only or their .cpp also survived: bt, btl4, btl4ver, btmssn, btreg, btteam, bttool, gauss, ppc, btl4arnd, btl4mode, testbt, turret.)

3c. Genuinely unaccounted-for (4) — please confirm with us (§7)

Module	Our handling	Question for you
btl4 (the WinMain/main app)	Recreated as btl4main.cpp, cloned from RP's launcher RPL4.CPP.	Is the real BT main app meaningfully different from RP's?
path	Not reconstructed. Not referenced on the current code path.	What is path.cpp — AI pathfinding? Is it needed for single-player bots?
mechbld	Assumed offline tool (mech/model builder), not runtime.	Correct?
btl4tool	Assumed offline tool, not runtime.	Correct?

3d. Missing files, organized by the directory you'd look in

This is the concrete "check your backup drive" list. BOTH = .cpp and .hpp both gone; .cpp only = header survived; .hpp only = implementation survived.

CODE/BT/BT/ (game logic)

File (module)	What's missing
mech, mech2, mech3, mech4, mechsub	BOTH
heat, powersub, gnrator	BOTH
mechweap, emitter, projweap, missile, projtile, ammobin	BOTH
gyro, torso, myomers, hud, dmgtable	BOTH
btplayer, mechmppr	BOTH
path	BOTH (AI pathfinding — see §3c)
mechdmg, mechtech, sensor, messmgr, mislanch, misthrst, seeker, btdirect	.cpp only
btcnsl	.hpp only

CODE/BT/BT_L4/ (app / cockpit / L4 integration)

File (module)	What's missing
btl4vid, btl4gaug, btl4gau2, btl4gau3, btl4mppr	BOTH
mechbld, btl4tool	BOTH (assumed offline tools — see §3c)
btl4 (main app), btl4app, btl4mssn, btl4rdr, btl4grnd, btl4pb, btl4galm	.cpp only

Present and intact (no help needed): CODE/BT/BT/: btmssn, btreg, btteam, bttool, gauss, ppc, turret.hpp, bt.hpp · CODE/BT/BT_L4/: btl4arnd, btl4mode, btl4.hpp, btl4ver.hpp, testbt.hpp.

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4. How the BT game logic is being reconstructed

BTL4OPT.EXE is a near-ideal target: class names, Class::Method strings, and original source paths in asserts (d:\tesla_bt\bt\mech.cpp) are left in the binary. Per module:

1. Locate the module's function cluster in the decompiled output (asserts + address contiguity).
2. Map vtable slots → methods (vtable order = declaration order, from the surviving header).
3. Map this+0xNN offsets → named members (from the header layout).
4. Rewrite the Ghidra pseudo-C into compilable C++, cross-checking the Red Planet analog for idioms — VTV≈Mech, VTVMPPR≈mechmppr, RPPLAYER/BLOCKER≈btplayer, WEAPSYS≈weapons, RPL4*≈the BT_L4 app layer.
5. Verify behavior against the binary as an oracle.

Result is a behavior-equivalent reconstruction, not the original text. Reconstructed files carry a header banner citing the originating @ADDR and the cross-references used.

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5. How it's assembled & patched into a running build

• Engine: the WinTesla MUNGA + MUNGA_L4 (193 files) compiles green to munga_engine.lib (modern MSVC, Win32, targeting the legacy DirectX SDK June 2010 for d3dx9/dinput).
• BT game lib (bt410_l4): the 43 reconstructed .cpp + the ~10 surviving BT .cpp + a small btstubs.cpp (see below) + a header-forwarding shim (the DOS-era code uses .hpp include names; WinTesla renamed engine headers to .h).
• Launcher: btl4main.cpp (WinMain, cloned from RPL4.CPP), drives BTL4Application.
• Link: bt410_l4 + munga_engine.lib + OpenAL/libsndfile + D3D9/d3dx9/dinput8 → btl4.exe.

The patch points we know about (the bring-up worklist)

These are deliberately isolated and flagged // TODO(bring-up):

• btstubs.cpp — first-link placeholders for: a handful of engine data globals not pulled from the static lib (allPresets, FrameTimeScale); the BT renderable pipeline (BT*Renderable); the 2D HUD layer (dpl2d_*, which libDPL provided and L4D3D hasn't yet re-implemented); a few Mech/subsystem accessors. Each is inert until given a real body.
• Two stubbed video data files — VIDEO\REPLACEMATS.tbl / MATREPLACETABLE.tbl (WinTesla-era material-substitution tables, absent from the 1995 content) created empty so video init proceeds.
• A few reconstructed BTPlayer/Mech methods still missing real bodies (currently being recovered, in dependency order driven by what the running game asks for next).

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6. Current runtime state (live)

btl4.exe boots cleanly: opens BTL4.RES, parses the -egg TEST.EGG mission (BattleTech / cavern / freeforall / night), creates the application, initializes the D3D video renderer, opens its window, and enters the mission simulation. The player-spawn pipeline now executes end-to-end — HuntForDropZone → DropZone reply → BTPlayer::CreatePlayerVehicle → MakeAndLinkViewpointEntity → Mech::Make → Mech::Mech (all reconstructed from the binary + RP analog this session).

Current frontier = the Mech object-layout + resource-streaming reconstruction. The Mech constructor runs but doesn't yet stream its model/subsystems/skeleton: in the reconstruction the resource layer (ResourceFind/ResourceStream) is still a no-op placeholder, and ~145 raw this[0xNN] field accesses in mech.cpp are backed by a shared scratch bank instead of named members. This is the single biggest remaining reconstruction task — and, notably, it's exactly the module whose original .hpp and .cpp were both lost (mech, see §3d). Recovering the real mech.* would short-circuit this entire pass.

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7. What would help most from you

1. The real BT game source — if a backup/dev drive has CODE/BT/BT/*.cpp (the lost mech, subsystems, weapons, HUD, app), it would replace the entire reconstruction. Even a partial set shrinks the work dramatically.
2. path.cpp — what is it (AI pathfinding?), and is it needed for single-player bot missions?
3. mechbld / btl4tool — confirm these are offline tools, not runtime modules.
4. The mission/egg flow for standalone (non-networked) play — anything special about how a pod launched a single mission vs. the multiplayer console handshake.
5. The 2D HUD / dpl2d_* layer — how the cockpit gauges/radar were drawn, since that's the part of libDPL the Direct3D port hasn't reproduced yet.
6. Confirmation that the pod disk image is the complete content master, and whether the full walk/run animation set exists beyond what shipped in the source archive.

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Reference docs in this repo: CLAUDE.md (overall project), btbuild/RECONCILE.md (the detailed reconstruction + bring-up ledger), decomp/README.md (decompilation method).