Field model formats

A field model is five file kinds working together:

Kind	Holds
.hrc	The skeleton — a bone tree, each joint naming an RSD
.rsd	A resource file naming one P mesh and its textures
.p	The polygon mesh
.tex	A texture page
.a	An animation — per-frame bone rotations

All five parse and re-serialize byte-identically across 30,590 files — char.lgp, magic.lgp, the minigames and the world map.

Nothing is skinned

Each joint carries a separate rigid mesh bolted to it. That is why the engine can hang any head on any body, and it is what makes part-swapping a data operation rather than a modelling one: a part fits any skeleton that has the same joint.

Key parts by joint name, not index

179 retail humanoids are exactly the standard 21-bone skeleton. Another 28 are that same skeleton with extra joints threaded in — kami for hair, ribon_a and ribon_b for Yuffie's ribbon, armer for Tifa. Aerith, Sephiroth, Reno and Hojo are among them.

Only one of those 28 keeps the humanoid bones in the same order. So anything keyed by bone index excludes 27 models for no reason. Keyed by joint name they belong with everyone else, they can trade parts with every other humanoid, and their extra joints simply appear as extra slots — which is how hair becomes a swappable mesh rather than only a colour.

Animations index bones by the file's own order, so bone order must never be rewritten even though lookup is by name.

Nothing here names anything

The archive labels none of this. A model is ajif.hrc, a mesh is ajje, an animation is acfe.a, and a face is a 32×32 texture with no label at all. 1,840 humanoid animations have no name anywhere, and no file records which closed-eye texture pairs with which open one.

Naming is therefore editorial work, which is exactly why it lives in this wiki: the entity pages carry the bindings (see [[canon/person/cloud-strife]] for the shape), and _index/ carries the full member tables.