Sylpheed/docs/re/structures/unit-substructure-records.md

# ✅ The destructible-subsystem model — a unit's sub-records

The corpus has named the sub-records of a unit `.tbl` since
[unit-struct-runtime](unit-struct-runtime.md) ("`Generic`, `Maneuver`,
`Shield`, `Explosion`, `Mass`, `Effect`, `SE`, `Turret_00N` … all flattened
into that single object") but has never **opened** them. This does.

One unit = one IDXD pak entry. 114 of them
([the `Generic` partition](unit-datasheet-static.md)). Artefact
`../data/unit-substructures.txt`, regenerator
`tools/re-capture/unit_substructures.py`.

| family | records | max/unit | non-indexed fields |
|---|---:|---:|---:|
| `Turret_NNN` | **835** | 63 | 38 |
| `Generic` / `Maneuver` / `Effect` / `Shield` / `Mass` / `SE` / `Explosion` / `StructureCount` | 114 each | 1 | — |
| `NS_Body` | 68 | 1 | 12 |
| `ShieldGenerator_NNN` | 46 | 4 | 21 |
| `Thruster_NNN` | 38 | 4 | 21 |
| `Hatch_NNN` | 26 | 4 | 23 |
| `Bridge_NNN` | 25 | 2 | 20 |

Seven singletons named with a literal `???` (`Turret_???`, `Versatile_???`, …)
are the schema's own template rows.

## The shared destructible-part base

`Turret`, `ShieldGenerator`, `Thruster`, `Hatch` and `Bridge` are the **same
record shape** with per-kind extras. Every one of the 970 part records carries:

```
ID  Name  ParentStructureID  Frame  NomalModel  CollisionModel  Radius
HP  IsDestructible  IsShielded  IsInvolved  IsRadarVisible  SpreadDamage
DamagedMotionName  DestroyMotionName  DestroyMotionTime
Effect_Explosion  Effect_Flare  Effect_Paralyze
```

(`NomalModel` is the game's own spelling.) `Frame` is a **mesh node name** —
`GN_mnt` on the player craft — so a part is bolted to a named bone of the
`Generic.Model` mesh the corpus already decodes.

Per-kind, on top of that base:

| kind | extra fields |
|---|---|
| `Turret` | `WeaponID`, `AngularVelocity`, `YawLimit`, `PitchLimit_Elevation`, `PitchLimit_Depression`, `CoverArea`, `IsAuto`, `HasBarrel`, `CommonCannonModel`/`Frame`, `CannonModel_NNN`/`CannonFrame_NNN` (up to 80), `SequencingCount`, `SequencingInterval`, and on a few: `CurveAngle`, `FCSAngle`, `FollowView`, `ShellModel`, `CoverModel` |
| `ShieldGenerator` / `Thruster` / `Bridge` | `PowerRatio` — losing the part degrades the parent |
| `Thruster` | `NozzleCount` |
| `Hatch` | `SquadronID`, `LoadedCount`, `MaxAvailableCount`, `TakeoffInterval` — **a carrier's launch bay** |

🔑 That is a complete component model: named bone, own mesh and collision mesh,
own HP and destruction motion + effects, and a `PowerRatio` saying what the
parent loses when it dies.

## The one-record blocks

| record | fields |
|---|---|
| `Shield` | `MaxValue`, `ChargeSpeed`, `ChargeDelay`, `ChargeDelay_Break` |
| `Mass` | `DryMass`, `GrossMass` |
| `SE` | `ExplosionSE`, `Thruster`, `SideThruster`, `JumpIn`, `JumpOut`, `ShipEnvironmentSE`, `LowerHPSE`, `LowerHPThresholdRatio` |
| `Explosion` | `Delay`, `DelayAdjustment`, `ExplosionFxModel`, `ExplosionMotionName`, `LowerHPFxModel`, `DestroyMotionName`, `DestroyMotionTime` |
| `StructureCount` | `TurretCount`, `BridgeCount`, `HatchCount`, `ShieldGeneratorCount`, `ThrusterCount`, `VersatileCount` |
| `NS_Body` | `Model`, `NodeCount`, `Interval`, `StartingVelocity`, `Deceleration`, `Volume`, `Color_R/G/B`, `AttenuationVolume`, `AttenuationAlpha`, `DeleteFadeSpeed` — an engine-trail ribbon, on 68 of 114 |

Every field the runtime doc reached for `Shield` (`MaxValue +0x238`,
`ChargeSpeed +0x244`) and `Mass` (`DryMass +0x274`, `GrossMass +0x278`) is
here, at the same names.

## 🧪 Control 1 — `StructureCount` counts the part records

`declared == #<Kind>_NNN records`, over 114 units × 6 kinds = 684:

| | |
|---|---:|
| equal | **612** |
| declared 0, one blank placeholder record | 55 |
| differs | **11** |
| kind absent from `StructureCount` | 6 |

The 55 are a real sub-rule, not slack: a kind with a count of **0 still emits
exactly one record**, and all 55 have empty `Name`, `NomalModel` *and* `Frame`.
So the file always carries at least one slot per kind.

Every one of the 11 exceptions is a **`Turret`**, and every one has
`declared < records` — never the other way round. Nine are the player's
DeltaSaber family:

```
declared=4  records=63   x7   f001_T, f001_T_EX5, f001_T_EX5_el, f001_T_Player,
                              f002_W, f002_W_Player, f004_A_Player
declared=4  records=5    x2   f001_T_Player_Ttrl1 / _Ttrl2
declared=1  records=2    x1   UN_e001_ADAN_Elan_EX4
declared=8  records=9    x1   UN_e107_ADAN_AAFrigate_EX4
```

✅ **ADOPTED the next day** — on the player craft the `Turret_NNN` list is a
*hardpoint catalogue* and `TurretCount 4` is how many mount at once. The
Arsenal table proves it from an independent file: **59/59 of its items name a
`Turret_NNN` slot in `PlayerWeapon`**, see
[arsenal-item-weapon-chain](arsenal-item-weapon-chain.md). The two `+1`
warship/craft cases are still unexplained.

⚠️ The "10 distinct `WeaponID`s" measured here is the **AI** variant
`UN_f001_TCAF_DeltaSaber_T`. The `_Player` variants give the same 59 slots
**59 distinct** weapon records — wingmen fly a collapsed 10-class set.

## 🧪 Control 2 — turret weapons resolve into the weapon datasheet

**835 / 835 `Turret_NNN.WeaponID` values are an `ID` in the 131-record
`Weapon` table. Zero unresolved.** 105 distinct values are used; **26 of the
131 weapons are never mounted on a turret** — the player-only arsenal.

That is a hard cross-table link: [the weapon
datasheet](weapon-datasheet-static.md) is what arms every gun on every ship.

## ❌ Refuted in the same pass — "the 59 hardpoints are the 59-name arsenal roster"

The DeltaSaber's 63 turret slots hold **59 non-`Weapon_NULL`** entries, and the
`WEAPONS` roster in `GP_HANGAR_ARSENAL.pak` has exactly **59** names. Tempting,
and wrong: the two sets **overlap in 0 values**, and the 59 slots carry only
**10 distinct** `WeaponID`s. The roster is display names
(`Machiene_Cannon_MG1` — the game's spelling); the hardpoints reference
`Weapon.ID` (`Weapon_TCAF_DeltaSaber_Gun`). Two namespaces, one coincidence of
count.

## ✅ `CoverArea` is a 6-bit mount mask — and the other three leftovers

Artefact `../data/turret-coverarea.txt`, regenerator
`tools/re-capture/turret_coverarea.py`.

**Six bits, never more.** Across all **835** turrets: 41 distinct values, max
`0x3f`, **bits 6 and 7 set on none**. Per-bit counts 709 / 117 / 274 / 274 / 260
/ 237; popcounts 0…6.

| mask | n | what |
|---|---:|---|
| `0x00` | 34 | the empty `Weapon_NULL` hardpoints — `YawLimit 0` on all 34 |
| `0x01` (one bit) | 439 | craft hardpoints — `YawLimit` 2.5 / 1.0 / 0 |
| 2–6 bits | 362 | warship mounts — `YawLimit` 45…180, real pitch limits |

🔑 **It tracks the MOUNT, not the weapon.** `UN_e107_ADAN_AAFrigate` carries
eight identical `..._AAFrigate_AAGun` turrets: `GN_GunXS_01…04` are **`0x1d`**
and `GN_GunXS_05…08` are **`0x2d`** — same gun, same `YawLimit 120`, different
mask. `UN_f104_TCAF_Battleship` spreads five masks (`0x1d`, `0x39`, `0x35`,
`0x27`, `0x2b`) across `GN_TGunL_01…05` / `GN_TGunM_02…03`, all firing the same
`CAF_Ship_ASGun`.

🟡 **Which physical sector each bit denotes is NOT determined.** Six bits and a
field called *CoverArea* invite ±X/±Y/±Z or six hull faces, and the 01–04 /
05–08 split above looks like a side — but nothing static fixes the axis
convention. **A reading, not adopted.** ❌ Also refuted on the way: bits 2 and 3
are not a mutually-exclusive pair — 188 turrets set both.

### The 26 weapons no turret mounts

`Weapon.ID` 131, mounted 105, never **26** — and they are a coherent set, not
strays: **11 `_P` player variants** (`…_Beam_P`, `_Gun_P`, `_Bomb_P`, …),
the **nose and twin mounts** (`_NoseGun`, `_NoseGun_P`, `_NoseGun_None`,
`_NoseGun_Ttrl`, `_TwinGun`, `_TwinGun_P`), **two `_Child` sub-munitions**
(`wep_13`, `wep_29`), the **three `S16Boss_*`** weapons, three `Weapon_Test_*`,
and `ADAN_Attacker_S_GunTurret`.

### `Versatile_NNN` ships nowhere

**0 populated records across all 41 archives** — only the `???` template row.
The schema declares a sixth destructible-part kind with zero instances.

### The two units one turret short — both extras are MISSILE mounts with no frame

* `UN_e001_ADAN_Elan_EX4`: `TurretCount 1`, two records — `Turret_000`
  `…Turret_NoseGun` and `Turret_001` `…Turret_Missile`, both mask `0x01`, both
  with an empty `Frame`.
* `UN_e107_ADAN_AAFrigate_EX4`: `TurretCount 8`, nine records — eight
  `GN_GunXS_0N_ContH` gun turrets, plus one `…Ship_AAMissile` at mask `0x0c`
  **with no `Frame` at all**.

🔑 In both, the uncounted extra is a **missile launcher with no mesh node** — so
`TurretCount` counts frame-mounted guns, and a frameless launcher rides in the
same record family without being counted. Consistent across both, n=2, so
**stated as the observed pattern, not a rule**.

## 🟡 Not settled

* What links a roster entry to a `Weapon.ID` — the 59-of-131 question is still
  open, and this pass shows the answer is **not** the hardpoint list.
* `Versatile_NNN` has 0 populated records in this pak; only the `???` template
  row exists, so its schema is known and its instances are not.
* ~~`CoverArea` reads as a hex word — a bit mask, bits unknown.~~ **Opened
  above**: a 6-bit mount mask. Which sector each bit means is still open.
* The 6 `no field` comparisons are one unit whose `StructureCount` omits every
  count.

## ✅ Every effect a datasheet binds, against every effect the LOD tables declare

The `Explosion` substructure's field list is already above; what was untested is
whether its `ExplosionFxModel` — and the whole effect-binder family — actually
*resolves*. Run as a declared × used partition, sweeping **34 binder field
names** (`*FxModel*`, `*EffectName`, `Effect_*`, `ShellModel`, `CoverModel`,
`SilhouetteModel`) against every name declared by a `LOD_Effect_<n>` or
`GameModel_<n>` field anywhere on the disc:

| | declared | not declared |
|---|---|---|
| **used** | **172** | **58** |
| **not used** | **318** | — |

490 declared, 230 used. The top binders are `Effect_Paralyze` (2 874 values),
`ShellModel` (996), `HitFxModel` (738), `JetFxModel_000` (408),
`MuzzleFlashFxModel_Loop` (384).

🔑 **The 58-cell is almost one field.** 53 of the 58 are bound by
**`SilhouetteModel`** alone, and all 53 are `rou_f###_wep*` names — the arsenal
item silhouettes already documented in [[arsenal-item-weapon-chain]]. They are
undeclared because they are **the wrong kind**: each resolves as its own
standalone package, e.g. `rou_f001_wep_01.xpr`, and never as a LOD-table entry.
Nothing is missing — the sweep was reading an asset-file name as if it were an
effect name.

That leaves **four genuinely undeclared effects** — `eff_e0044`
(`ExplosionFxModel`), `eff_f0002` + `eff_f0002_barn` (`JetFxModel_00N` /
`AfterBurnerFxModel_00N`) and `eff_h308` (`HitFxModel`) — plus one placeholder
(below). None of the four resolves as a record name or a field name either.

⚠️ Controls, both from the previous iteration and both reproduced: `eff_n0071`
is **declared and used 6×** (= one user, per the per-pak-copy rule);
`eff_e0033` is **declared and used 0×**, i.e. it sits in the 318-cell. The 318
is expected rather than alarming — the `EnumLODSet`/`EnumGameModel` family is
overwhelmingly *equipment*, so most of what it declares no unit datasheet binds.

### 🔑 A Shift-JIS dev placeholder: `文字列`

One "effect name" in the 58-cell is not a name at all. Bound by
`Effect_Explosion` and `Effect_Flare`, **72 occurrences = 12 users**, its bytes
are `95 B6 8E 9A 97 F1` — Shift-JIS for **`文字列`**, literally *"character
string"*. It is the placeholder a developer left in the field.

⚠️ **Reader defect this exposes:** `tools/re-capture/unitgroup.py` hands the
value back as Latin-1 mojibake (`¶ñ`), so an IDXD string field can carry
**Shift-JIS** and our decode does not know it. Worth fixing before any of these
strings reach a port; harmless for name-matching, because every other value in
the corpus is ASCII.

### ✅ `_hangar` *is* a package-naming convention — 59 of 166, zero partials

Following the silhouettes into the ISO tree: **59 of the 166 `.xpr` packages end
`_hangar.xpr`, and 59 of 59 have a bare twin** of the same stem. So a model
shown in the hangar ships as a second package beside the in-flight one.

This is the direct contrast to the previous iteration's refutation — `_all` /
`_child` was **1** of 166 with one stem and is not a convention; `_hangar` is
**59** of 166 with zero partials and is. Suffix conventions in this corpus are
worth testing precisely because they are not all real.

### ❌ An `.xpr` byte search cannot answer "does this effect ship"

Testing the four genuinely-undeclared effects against the 166 `.xpr` packages
gave `eff_f0002` and `eff_f0002_barn` in `Base.xpr`, and nothing for `eff_e0044`
or `eff_h308`. **But the control refutes the instrument, not the effects:**
`eff_n0071` — measured *live*, bound by an `Explosion` record's
`ExplosionFxModel` — **also returns nothing** from the same search.

A known-live name the test cannot find means the test has no power here. So:

* `eff_f0002` / `eff_f0002_barn` **do** have a mesh in `Base.xpr` (presence is
  still evidence when it is positive);
* nothing follows about `eff_e0044` or `eff_h308`, and the earlier remark that
  `eff_e0058`, `eff_e0059` and `eff_e0060` "have no mesh" should be read the same
  way — **absent from a byte search over `.xpr` is not absent from the disc**.

Whatever ships `eff_n0071` is not a plain name string inside those 166 files,
so effect meshes must be reached some other way. Finding that route is the open
question; until then, only the positive half of this test counts.