# START HERE — V385 Minimal Resolved Figure four Proof

Status: NUMERIC/CPU PROOF PASS. CHROMIUM/OPENGL VISUAL QA PENDING.

## Read order

1. `START_HERE_V385_MINIMAL_RESOLVED_FIGURE_FOUR_PROOF.md`
2. `HANDOVER_V385_MINIMAL_RESOLVED_FIGURE_FOUR_PROOF.md`
3. `CURRENT_STEP_V385_MINIMAL_RESOLVED_FIGURE_FOUR_PROOF.md`
4. `V385_MINIMAL_RESOLVED_FIGURE_FOUR_PROOF_MANIFEST.json`
5. `HANDOVER_V385_RESOLVED_EXERCISE_BANK_ARCHITECTURE.md`

## Result

V385 proves a separate resolved playback path for `figure-fours` without changing any V384E129 pose, IK, grip, contact, finger or production-player source.

The authoring runtime bakes 480 normalized phase samples from the actual Nex FBX. Playback applies stored model/root transforms and local bone quaternions only. It does not call live IK, CCD, grip, finger or QA solvers.

## Numeric proof

- Exact baked sample maximum world-space bone error: `8.343167878641977e-8 m`.
- Between-sample maximum world-space bone error: `0.0053224242173198 m`.
- Authored-event-window maximum world-space bone error: `0.008085910945109718 m`.
- Local CPU test: live solve average `18.7783 ms`; resolved playback average `0.0850 ms`; speedup `220.86x`.
- Both Figure four peak frames were baked from generic two-hand grip results with `gripCount=2` and both sides passing.

See `diagnostics/v385/V385_RESOLVED_FIGURE_FOUR_NUMERIC_QA.json`.

## Important temporal finding

The first naive interpolation attempt failed by up to 17.29 cm because the existing live runtime treats authored contact keyposes as discrete events. V385 therefore does not interpolate through those event frames. Grip events preserve the existing `±0.001` phase activation window; other authored keyposes are exact boundaries and are skipped by neighboring interpolation.

This reproduces current runtime semantics. It does not invent longer grip/contact hold windows.

## Prototype player

`assets/nexprod/nexprod01-resolved-player-v385.html`

Example:

```text
assets/nexprod/nexprod01-resolved-player-v385.html?exercise=figure-fours&caseId=v93_warmup_figure_four_walk_1&phase=0.25&play=0&safeBoot=0&visualMode=nex
```

## Stop boundary

Do not replace the production player or bake the remaining exercise bank from this proof until Chromium/OpenGL visual QA confirms the actual skinned Nex result and the current short grip-event timing is explicitly accepted or separately authored.