phase2/phase2_report.md

# Phase 2 — Motion-NDF window ablation report

> ⚠️ **SYNTHETIC PROXY MODE** — trained on the synthetic manifold (gated AMASS, docs/BLOCKERS.md).
> Demonstrates the *mechanism* (H3): why poses must be lifted to motion windows. Not the final
> scientific numbers — re-run on AMASS windows for those.

Window `W = 9` (+ joint velocity).

## AUROC(valid vs negative) — higher = better separation; 0.5 = blind

| negative type | static W=1 | Motion-NDF (W+vel) |
|---|---|---|
| shuffled (dynamics-wrong, same poses) | 0.498 | **1.000** |
| highvel (dynamics-wrong, fast) | 1.000 | **1.000** |
| pose_ood (off-manifold poses) | 1.000 | 1.000 |

![ablation](phase2_ablation.png)

## Takeaway
The static field sits near **chance (0.5)** on the dynamics-wrong negatives (shuffled / highvel) — the
per-frame poses are identical, so a pose-only field cannot tell smooth motion from broken motion.
Motion-NDF, seeing the window + velocity, separates them (gain shuffled **+0.502**,
highvel **+0.000**). Both catch off-manifold poses. This is the
justification for Phase 2 and motivates including velocity in the reward (Phase 1 `use_velocity`).