# NPC proportion audit

Status: audited 2026-11-02. All eight library variants are inside the stylized
proportion guide; no geometry correction was required in this pass. The report
is repeatable from the exported GLBs:

```bash
python3 tools/npc_proportions.py report
python3 tools/npc_proportions.py report --json
```

## Method

`tools/npc_proportions.py` reads the GLB meshes and rest-pose joint hierarchy:

- height from the full mesh bounds;
- head height, width and aspect from `Head`/`skin` vertices (hair excluded so
  long hairstyles do not change the head measurement);
- shoulder silhouette from vertices in the upper-chest band around the
  shoulder joint;
- hip width from `HipL`/`HipR` pants vertices;
- torso length from the Spine joint to the shoulder joint;
- leg length from the Spine joint to the lowest vertex;
- arm length from the shoulder joint to the Hand joint;
- foot length from the forward extent of the KneeL/KneeR shoe vertices.

All ratios are divided by total standing height except `head_aspect`
(width / head height).

## Guide

These are stylized-but-credible bands for the game's low-poly adults, not
photoreal anatomy. The broad build is allowed a larger shoulder/hip silhouette
than the slim build.

| Ratio | Target | Notes |
| --- | ---: | --- |
| `head_height` | 0.16–0.22 | deliberately larger than a realistic 0.13–0.15 |
| `head_aspect` | 0.70–1.00 | width / height; rounded heads are acceptable |
| `shoulder_width` | 0.28–0.38 | silhouette includes sleeves and build scaling |
| `hip_width` | 0.17–0.23 | pants-only width, not skirt/coat flare |
| `torso_length` | 0.28–0.38 | Spine joint to shoulder |
| `leg_length` | 0.40–0.48 | Spine joint to ground |
| `arm_length` | 0.28–0.38 | shoulder to hand |
| `foot_length` | 0.12–0.18 | shoe forward extent |

## Result

| Character | Height | Head | Aspect | Shoulder | Hip | Torso | Leg | Arm | Foot | Result |
| --- | ---: | ---: | ---: | ---: | ---: | ---: | ---: | ---: | ---: | --- |
| `npc_casual` | 1.824 m | 0.190 | 0.907 | 0.320 | 0.209 | 0.307 | 0.449 | 0.329 | 0.144 | PASS |
| `npc_jacket` | 1.824 m | 0.190 | 0.907 | 0.325 | 0.209 | 0.307 | 0.449 | 0.329 | 0.144 | PASS |
| `npc_coat` | 1.824 m | 0.190 | 0.907 | 0.329 | 0.209 | 0.307 | 0.449 | 0.329 | 0.144 | PASS |
| `npc_vest` | 1.819 m | 0.191 | 0.907 | 0.321 | 0.210 | 0.308 | 0.451 | 0.330 | 0.144 | PASS |
| `npc_dress` | 1.825 m | 0.190 | 0.907 | 0.287 | 0.191 | 0.307 | 0.449 | 0.329 | 0.144 | PASS |
| `npc_hoodie` | 1.856 m | 0.187 | 0.907 | 0.320 | 0.205 | 0.302 | 0.442 | 0.323 | 0.141 | PASS |
| `npc_firefighter` | 1.819 m | 0.191 | 0.907 | 0.356 | 0.225 | 0.308 | 0.451 | 0.330 | 0.148 | PASS |
| `npc_guard` | 1.819 m | 0.191 | 0.907 | 0.370 | 0.219 | 0.308 | 0.451 | 0.330 | 0.144 | PASS |

No variant is outside a band, so the body pass does not need a global skeleton
or mesh rescale. The values closest to a boundary are:

- **head height 0.190** against the 0.22 upper bound, and **head aspect 0.907**
  against 1.00 — the head is deliberately large. Any head-size change must be
  coordinated with the face/headgear pass and its gear-fit measurements.
- **guard shoulder 0.370** and **firefighter hip 0.225** against the broad-build
  upper bounds — these are the intended uniform/turnout silhouettes, not
  outliers.
- **leg length 0.449** and **torso 0.307** sit inside the guide for all variants;
  the earlier short-leg impression came from the hip joint position, not the
  visible pelvis line.

## Follow-up

The proportion audit does not replace the visual criteria in
[`npc-visual-review.md`](npc-visual-review.md): neck/shoulder/hip transitions,
face depth, hand grips, clothing hems and shoes still need the appearance pass.
Re-run the audit after any body mesh or skeleton change and record the new
ratios here.