Add reviewed MakeHuman head prototype (vision gate rejected)

docs/makehuman-head-review.md

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+# MakeHuman head prototype
+
+Status: **local prototype, rejected by the automated visual gate, not integrated.**
+The asset is a standalone head/neck extracted from the CC0 MakeHuman base in
+`tmp/npc-research/makehuman/base.obj`. It is kept as a reviewable experiment and
+is not part of the shipped NPC contract.
+
+## Asset
+
+- GLB: [`assets/models/blender_src/makehuman_head.glb`](../assets/models/blender_src/makehuman_head.glb)
+- Review sheet: [`blender_previews/sheet_makehuman_head.jpg`](blender_previews/sheet_makehuman_head.jpg)
+- Source workflow (development-only): `tmp/npc-research/build_makehuman_head.py`
+  — extracts the MakeHuman head, cuts it at the neck, keeps the head/eye/mouth
+  components, cuts an almond aperture through a skin eyelid mask, adds recessed
+  eyeballs with flat iris/pupil discs, anchors brows to the face surface, renders
+  front/three-quarter/profile and exports the standalone GLB.
+- Measurements (final build, `inspect`): **12,641 triangles / 7,690 split
+  vertices**; bounds approximately `x ±0.094 m`, `y -0.180…0.042 m`,
+  `z 1.530…1.803 m` in project Z-up space. It is inside the 16,000/16,000
+  character cap.
+- Materials used: `skin`, `eye_white`, `iris`, `pupil`, `hair`. No textures are
+  baked into this prototype.
+
+![MakeHuman head review sheet](blender_previews/sheet_makehuman_head.jpg)
+
+## What was done
+
+1. Imported the CC0 MakeHuman base OBJ and cleared the importer axis rotation.
+2. Applied the project scale/axis transform: 1.82 m body, Z-up, metres,
+   front −Y.
+3. Cut the head at the neck (`z ≈ 1.53`) rather than keeping the cut shoulders;
+   capped the neck opening.
+4. Built an eyelid mask by subtracting an almond aperture from a skin sphere
+   centred on each eye (`solver = "EXACT"`), then recessed the globes so the
+   cornea sits behind the lid plane.
+5. Added flat iris/pupil discs on the globe axis; disabled backface culling so
+   the discs stay visible at three-quarter angles.
+6. Anchored brow strips to the skin with object-space ray casts and added a
+   shallow supraorbital ridge so they do not float, then reduced the crown
+   height to improve the profile silhouette.
+7. Fixed a material-remap bug introduced by joining the extra eye objects: the
+   joined head faces were pointing at the `eye_white` slot, making the whole
+   head render as white clay. The largest connected component is now forced
+   back onto `skin` after the join.
+8. Rendered front/three-quarter/profile views in a neutral review studio and
+   exported the standalone GLB.
+
+## Provenance
+
+- Base mesh: MakeHuman / MPFB base, CC0, from the local research set
+  `tmp/npc-research/makehuman/`; see [`CREDITS.md`](../CREDITS.md).
+- The head is a **derived prototype**, not a shipped NPC. It does not enter
+  `assets/models/blender/npc/`, `npc_base`, the runtime `NpcAvatar` path, CI, or
+  a release package until the NPC overhaul plan accepts it.
+- Source photographs/proportions are not used as textures here; this is a
+  geometry-only head built from the researched model data.
+
+## Review criteria
+
+Accept only if:
+
+- the head reads as human at front/three-quarter/profile and the neck is a
+  clean head/bust silhouette, not a shoulder cut;
+- eyes, brow, nose, mouth and ears are readable without spikes, holes or
+  floating shells;
+- the asset is inside the character budget and has no script/contract violation;
+- the prototype remains clearly local and un-integrated until the part pipeline
+  is approved.
+
+## Judge result
+
+**VERDICT: REJECT** (vision judge `z-ai/glm-5.3-flash`, final build render set
+above). The gate is blocked; the prototype is not presented as an accepted head.
+
+Blocking findings:
+
+- **P0 — globe depth is inconsistent across views.** The front/three-quarter
+  reads still show a bead-like iris with a pale sclera halo, while the profile
+  reduces the eye to a brown sliver. The judge reads this as a faked recess
+  rather than a socketed globe under a lid.
+- **P0 — no convincing lid overlap.** The iris remains nearly circular in front
+  and the upper lid does not visibly clip the globe; the skin lid mask reads as
+  a crater around a bead.
+- **P0 — iris orientation reads decal-locked** at three-quarter, so the gaze
+  appears to drift off the head axis.
+- **P0 — the aperture/lid mask is too circular** and lacks medial/lateral
+  canthi, so the eye still reads as a doll eye at portrait distance.
+
+Should-fix findings:
+
+- the brow tubes are better anchored but the medial ends still detach in
+  three-quarter/profile;
+- nose lacks a defined tip/wing and nostrils;
+- mouth is a faint geometric seam with no lip volume;
+- crown/back-of-skull is still faceted and egg-like in profile;
+- the catchlight is baked geometry and is not consistent between eyes.
+
+What passed: the skin/eye material remap is correct, the eye openings are
+closed, the standalone GLB reports **12,641 triangles / 7,690 split vertices**
+with no issues, and an assembled `npc_casual` with this head passes `inspect` at
+**15,532 / 16,000 triangles, 13,310 split vertices, 14 bones, no issues**.
+
+Known limits: bald mannequin-like presentation, stylized geometry-only
+iris/pupil, no rig, no UV texture pass, and the neck cap is a review cut rather
+than a body-welded seam.
+
+## Next steps after the gate passes
+
+- Replace the radial lid mask with real upper/lower lid masses that fold over
+  the globe, with pointed canthi, and pass the profile view.
+- Move the iris onto a curved cornea cap so its orientation follows the globe at
+  three-quarter angles, and use a lighting-driven catchlight instead of baked
+  white geometry.
+- Compare against the project `_face` baseline and decide whether this head is
+  the base for the local head/face overhaul.
+- Add a clean UV/material pass and a contract armature/weights if it becomes
+  part of a library character.
+- Keep the source script under `tmp/`; promote only the reviewed GLB and durable
+  docs/preview sheet.