Refit the backpack straps for both torsos (ADR-0018)

TODO.md

@@ -775,29 +775,44 @@ blocked rig can no longer block the whole release.
       (pose-rotate → apply modifier → reset pose → edit-mode rotate arms → re-add modifier →
       export `export_apply=False`) now yields a correct arm-down base: Blender deformed x ±0.221
       and the rest bone tail points down. Still local (`tmp/`), not shipped.
-- [x] Re-derive the pose composition for a non-180° rest. Godot's `set_bone_pose_rotation` is
-      rest-relative, so `rest * Quaternion(axis, angle)` only reproduces the old rig by accident
-      (the old rest is 180°, so `rest² = identity`); the Quaternius ~76° rest breaks it. Fixed in
-      commit `8b1bf73`: `rest * Quaternion(rest.inverse() * axis, angle)` — backward-compatible
-      (the old 180° rest maps the axis to itself). Godot 277/277.
-- [ ] Godot skinning import: root causes found and narrowed. (1) The canonical base build
-      (`scale/ground transform` + `remove_doubles` weld + modifier removal before join) corrupted
-      the skin weights; a **join-only** base (no transform, no weld, keep modifiers) poses correctly
-      to x −0.228/0.228. Use `tmp/npc-research/build_base_minimal.py`.
-      (2) Fixed: the arm-down bake (`bake_armdown_v5.py` — pose, read pose matrices, apply modifier,
-      **reset pose to identity**, set rest matrices, re-add modifier) now bakes correctly
-      (DEFORMED x −0.228/0.228, Godot bind_pose down). `NpcAvatar` now also has the side swap,
-      the arm swing axis (LEFT) and the hand-proxy position fix (`2a6f29f`). Remaining: the
-      handheld gear (camera) sits at the shoulder/chest instead of the wrist — re-derive the gear
-      attach offsets against the Quaternius skeleton, then the face/silhouette gate.
-- [ ] Add regression tests: a bone with a ~76° rest reaches a known global orientation; the
-      Quaternius joint map resolves; the 13-core fallback poses exactly as it does today.
+- [x] Re-derive the pose composition for a non-180° rest. Superseded by the rig-agnostic
+      `_swing_bone()` below: the rest-relative `set_bone_pose_rotation` form was never exact,
+      because `get_bone_rest()` is parent-relative and already carries the importer's axis
+      conversion. Kept in `MEMORY.md` as a rejected approach.
+- [x] Fix the skinning/rest bake end to end (commit `cd285b3`):
+      (1) the canonical base is **join-only** (`tmp/npc-research/build_base_minimal.py`: no
+      `remove_doubles` weld, no scale/ground transform, keep the Armature modifiers) — the weld
+      and the transform corrupted the Quaternius weights;
+      (2) the arm-down bake (`tmp/npc-research/bake_armdown_v5.py` — pose, read pose matrices,
+      apply modifier, **reset pose to identity**, set rest matrices, re-add modifier) bakes the
+      rest correctly (DEFORMED x −0.228/0.228, Godot bind pose arm-down);
+      (3) `NpcAvatar._swing_bone()` now writes the **global** bone pose from
+      `get_bone_global_rest()`, so one formula drives both the 62-joint Quaternius rig and the
+      13-core fallback (measured: posed bone axis matches the proxy pivot at dot 1.000 on the
+      Quaternius, and the procedural rigs are unchanged);
+      (4) `RIG_BONES` + `NpcAvatar.bone_name()` hold the only side mapping (the Quaternius labels
+      `L`/`R` opposite the project), and the hand proxy is `global_wrist − global_elbow`.
+      Verified in Godot: idle/sit/walk captures on npc_casual plus the unchanged procedural rigs.
+- [x] Add regression tests: `test_shipped_rig_resolves_the_animation_joints` covers the joint map,
+      the baked arm-down rest, the down-pointing arm axis and the proxy side mapping; the Blender
+      audit/`inspect` and `npc_proportions` now understand both rigs. Godot 278/278, Python
+      167/167.
+- [x] Give the Quaternius base the five tint slots: `build_base_minimal.py` renames the upstream
+      materials to `skin`/`cloth`/`pants`/`hair`/`accessory` and keeps `Eye`/`Eyebrows` as
+      fixed-colour detail. The source UV map is degenerate (every loop at 0,0), so the build now
+      Smart-UV-unwraps and repacks the layout — texel density went from an unmeasurable 0 to
+      73–74 px/m on the 256² maps and the 256² AO bake works again.
 - [ ] Verify Idle and Walk on the 62-joint rig: loop seam, foot contact, root motion and frame
       rate. Record which of the 24 clips are in scope and which stay unused.
 - [ ] Decide and record how poses the clips do not cover (seated, raise-hand, head turn) are
       driven at runtime.
 - [ ] Keep the fallback tested: `npc_base`, the MakeHuman head and `_build_body()` remain
-      selectable; no MPFB work is reopened and no Stage-1 proportion warp returns.
+      selectable; no MPFB work is reopened and no Stage-1 proportion warp returns. (The procedural
+      library is still the majority of `CHARACTER_POOLS` and captures clean, but the fallback path
+      itself has no dedicated test yet.)
+- [ ] Re-fit the remaining gear against the Quaternius torso: the `backpack` strap geometry was
+      authored for the old body width and now hangs in front of the chest. The camera was fixed
+      with a wrist strap (a neck strap floats when the item is hand-attached).
 
 ### Silhouette and face gate (owner)
 
@@ -814,10 +829,13 @@ blocked rig can no longer block the whole release.
 
 ### Pilot rollout
 
-- [ ] Map the five tint slots onto the Quaternius materials; unwrap per slot; bake 256²
-      AO/albedo/normal/ORM and check texel density.
-- [ ] Re-fit gear attach points against the Quaternius skeleton and test cap, helmet, backpack,
-      shoulder bag, lanyard, clipboard and firefighter tank.
+- [x] Map the five tint slots onto the Quaternius materials and unwrap the degenerate source
+      UV map; bake the 256² AO and check texel density (73–74 px/m).
+- [ ] Bake the per-slot albedo/normal/ORM maps and a per-slot atlas (the five slots currently
+      share one whole-body UV set).
+- [-] Re-fit gear attach points against the Quaternius skeleton and test cap, helmet, backpack,
+      shoulder bag, lanyard, clipboard and firefighter tank. (Camera done: wrist strap instead of
+      the floating neck strap. Backpack straps still cut across the Quaternius chest.)
 - [ ] Wire the approved base into one role (or the crowd roles if option b is chosen) with the
       procedural model as an instant fallback; no runtime download or optional dependency.
 - [ ] Run `blender_assets.py inspect`/`audit`/`fit`, `npc_proportions.py`, the 24-NPC budget smoke