# TORSO.CPP / .HPP — reconstruction notes

`Torso` (: PowerWatcher) drives torso twist (horizontal) and weapon elevation
(vertical). Tuning rates/limits stream from the resource
(`horizontal/verticalRotationPerSecond`, `horizontal/verticalLimit*`,
`torsoHorizontalEnabled`).

## Reconstructed

- Ctor: streams the base rates (deg→rad) + limits + `horizontalEnabled`, primes
  `currentTwist`/`currentElevation`/analog axes to 0, and installs
  `TorsoSimulation` as the per-frame Performance (the replicant copy is
  console-driven via `TorsoCopySimulation`, still staged).
- `analogElevationAxis` / `analogTwistAxis` members + `SetAnalogElevationAxis` /
  `SetAnalogTwistAxis` setters (written by `MechControlsMapper::InterpretControls`).
- `CurrentTwist()` / `CurrentElevation()` / `GetHorizontalEnabled()` accessors.
- `TorsoSimulation(Scalar)` — per-frame aim integration (authentic core):
  - `currentElevation += analogElevationAxis · baseElevationRate · dt`, clamped
    to [verticalLimitBottom, verticalLimitTop];
  - if `horizontalEnabled`: `currentTwist += analogTwistAxis · baseTwistRate ·
    dt`, clamped to [horizontalLimitLeft, horizontalLimitRight].

**VERIFIED** (`BT_MECH_LOG` `[mppr] torsoElev=`, forced-input `BT_FORCE_ELEV`):
stick pitch 0.8 slews the elevation up and clamps at the authentic
`verticalLimitTop` = 0.349 rad = **20°**. Zero Fail.

## Skeleton-joint binding (2026-07-21)

The twist joints are now RESOLVED and BOUND: the ctor calls
`owner->ResolveJoint(torsoHorizontalJoint / torsoHorizontalShadowJoint)` (the
skeleton is live — see MECH.NOTES.md), stores them as `Joint*`, and
`TorsoSimulation` pushes `currentTwist` onto `horizontalJointNode` via
`Joint::SetRotation` (hinge → `Radian`; ball → `EulerAngles` yaw).

The bring-up TEST.EGG mech has a FIXED torso (`horizJoint=''`, `enabled=0`), so
its twist path is inert — correctly guarded (null joint → no apply, no crash). A
torso-twist mech drives the joint. Verified headlessly; the VISUAL rotation
needs the renderer.

## Elevation does NOT drive a gun joint (corrected 2026-07-21)

Checked BT411 before reconstructing a "gun-elevation joint": no such joint
binding exists anywhere in the authentic engine. `currentElevation` instead
composes into `Mech::eyepointRotation` (the cockpit-eye / weapon-boresight
pitch) — see MECH.NOTES.md "PHASE 5.3 INCREMENT 5". `TorsoSimulation` only
needed to keep advancing the scalar state, which it already did; the missing
piece was the CONSUMER (`Mech::Simulate`'s eyepoint composition), now
reconstructed and verified (`torsoElev` == `eyePitch` every frame).

## Deferred

- HUD free-aim slew, the look-button state machine (`BTCommitLookState` /
  `gBTLookPitch`/`gBTLookYaw` — composes with elevation into the full
  eyepoint), `TorsoCopySimulation` (replicant console-driven aim) — still
  staged.