TeslaRel410/restoration/source410/BT/MECH.NOTES.md

MECH.CPP / .HPP — reconstruction notes

Status: Mech::Make (factory) reconstructed; the Mech constructor and the entire mech subsystem are the CURRENT FRONTIER — the largest remaining milestone in the reconstruction.

What is reconstructed

• Mech::Make(MakeMessage *) = return new Mech(creation_message); — the factory the registry / MakeAndLinkViewpointEntity calls.
• The static shared data (ClassDerivations / DefaultData) — from the earlier staging.
• A staged Mech ctor that chains the real JointedMover base ctor (so the model skeleton/segments stream from BTL4.RES) and then Fails.

The spawn factory path is now validated live: BTPlayer::CreatePlayerVehicle builds the Mech::MakeMessage, Application::MakeAndLinkViewpointEntity routes it through the registry to Mech::Make -> new Mech -> the JointedMover base ctor (real engine code, streams the mech model) -> the Mech ctor Fail. Boot reaches mech.cpp:66.

Why the Mech ctor is a milestone, not a brick

Mech::Mech is @004a1674, 5690 bytes — the largest single function in the game. It walks the model's segment table and instantiates the full subsystem roster (power, heat, weapons, actuators, controls, tech, damage zones), and primes ~150 members. Reconstructing it requires three things the tree does not yet have:

1. The complete 1995 Mech member layout as named fields. MECH.HPP currently carries int reserved[331] (1324 bytes) as a placeholder. BT411's Ghidra reconstruction sidesteps the layout entirely by writing raw offset pokes (Wword(0x104), *(void**)((char*)this + 0x388), this[0x14a]) — a WinTesla-port technique that CANNOT compile into a fresh 1995 build, where BC4.52 assigns offsets from the header declarations. So the layout must be derived as real members first.
2. The subsystem class hierarchy. MechSubsystem + derived: sensor, generator (gnrator), gyro, torso, HUD, myomers, plus the weapon subsystems (mechweap, ppc, gauss, projweap, mislanch, ammobin...). Of these, only GAUSS, PPC, SENSOR survive as source in the 4.10 archive (CODE/BT/BT); GNRATOR is a partial .TCP. The rest are part of the measured "917 missing functions" and come only from BT411's decomp.
3. The segment-table walk that reads the model resource and instantiates + wires each subsystem.

BT411's mech reconstruction is ~12,255 lines across mech.cpp / mech2 / mech3 / mech4 / mechsub alone, before the subsystem TUs — this is the bulk of the remaining game.

Reconstruction plan (for the dedicated mech milestone)

1. Derive the Mech member layout. Turn reserved[331] into named members. Sources: BT411's offset comments (this[0x14a] gyroSubsystem, +0x388 target entity, etc.) give the binary offsets; the embedded member types (NameFilter, AlarmIndicator, Slot/Socket, Reticle, Filter, CString, StateIndicator) come from the surviving MUNGA headers. Cross-check total size against the binary's new Mech allocation.
2. Reconstruct MechSubsystem base + the subsystem roster, backdating BT411 mechsub.cpp + the per-subsystem TUs; fold in the surviving 4.10 GAUSS/PPC/ SENSOR source where it exists (authoritative over the decomp).
3. Reconstruct the Mech ctor against the named layout: embedded-member construction, the segment-table walk, subsystem instantiation + wiring.
4. Then the per-frame path (mech2 animation SM, mech3, mech4 locomotion/ targeting) and the damage/weapon handlers.

Until then the ctor Fails cleanly at the frontier; everything below it (engine, app, network, mission, player, factory, jointed-mover base) runs real reconstructed code.