# SEQCTL.HPP / .CPP — reconstruction notes

**Status: struct + ctor/dtor + Init RECONSTRUCTED (compile-verified); the
per-frame playback methods (SelectSequence / Advance / Reset) staged. Helper
2/3 of the Mech embedded helpers ([[MECH-LAYOUT]] step 1).**

`SequenceController` — the BT keyframe-animation player embedded in the Mech as
`legAnimation` (@0x65c) and `bodyAnimation` (@0x6bc). Plays a gait clip: walks
keyframes, interpolates each animated joint's rotation, writes it through the
joint subsystem, returns the root-translation distance advanced. Absent from the
4.10 archive and the RP engine; reconstructed from the shipped binary + BT411's
seqctl.cpp decomp.

## What's real vs staged

- **Real (ctor-time):** default ctor (zeroes all fields) and `Init(Mech*)` — the
  Mech ctor calls `legAnimation.Init(this)` / `bodyAnimation.Init(this)`
  (binary; BT411 mech.cpp:685-686), so Init must run at construction. Init binds
  `owner` and caches `jointSubsystem = owner->GetJointSubsystem()`
  (JMOVER.HPP:104, returns `JointSubsystem*`), `clipResource = NULL`.
- **Staged (per-frame, after boot):** `SelectSequence` (@004277a8, clip parse +
  resource lock), `Advance` (@0042790c, keyframe interpolation + joint writes —
  the gait engine, ~145 lines in the decomp), `Reset` (@004283b8). These fire
  only once the mech is ticking, well past the current ctor frontier, so they
  Fail loudly until reconstructed.

## Field layout

Field set + order from BT411's binary-offset map (keyframeCount +0x14 …
callbackArg3 +0x50). Byte-exact offsets are not required for the functional
build (only wire/update-record layout needs that, and SequenceController is not
serialised) — the members are declared as named fields and BC4.52 lays them out;
the Mech's legAnimation/bodyAnimation slots size to `sizeof(SequenceController)`
self-consistently.

## Placement

1995 filename unknown (decomp-only; BT411 used seqctl.cpp). Filed as
BT/SEQCTL.HPP + SEQCTL.CPP. Not in the authentic BT.MAK member list, so the
build appends seqctl.obj to bt.lib via the extra-objs fallback (order is
immaterial — no static init).