mocapgod/docs/B_ENGINE_SETUP.md

Lane B engine — HSMR install & smoke-test state (session 3, 2026-07-17)

Engine per Decision 1 = Path B: HSMR → SKEL, run local on ultra, MPS. Installed under .engine/HSMR (gitignored). This doc = how it's wired + how to run once SKEL lands.

State

• ✅ uv venv py3.10 at .engine/HSMR/.venv; torch 2.13.0, mps.is_available() == True.
• ✅ Ungated weights in .engine/HSMR/data_inputs/: HSMR-ViTH ckpt (released_models/HSMR-ViTH-r1d1/checkpoints/hsmr.ckpt), ViTPose backbone, 3 regressors.
• ✅ Real person detector (torchvision Faster R-CNN, no detectron2) — checked by .engine/HSMR/test_detector.py, green today with no SKEL: 7/7 demo images → 15 patches @256×256 through HSMR's own cropper.
• ✅ Smoke-test runner .engine/HSMR/smoke_test.py — validated to the exact SKEL gate: imports + real detection + patch-crop all run; it fails only on the missing skel_male.pkl.
• 🚧 Blocked on the gated SKEL download (John's manual step, below) — the last thing standing.
• Install script (re-runnable): .engine/setup_hsmr.sh.
• ⚠️ The engine lives under .engine/ (gitignored) — the detector fix is on ultra's disk, not in git. Durable copies: vitdet/__init__.py, _headless.py, test_detector.py, and the smoke_test.py edits. A full re-clone of HSMR drops them; re-apply from this doc if that happens.

Apple-Silicon blockers — all three resolved (session 4, "Lane B detector")

• detectron2 won't build on ARM Mac → RESOLVED. Replaced its whole ViTDet detector with a torchvision Faster R-CNN drop-in in lib/modeling/pipelines/vitdet/__init__.py — same build_detector(...) -> (dets, downsample_ratios) contract, torchvision's person class (1) remapped to HSMR's human id (0), boxes as lurb, ratio 1.0. This also killed a load-time landmine: the old import detectron2 there exploded anything importing lib.kits.hsmr_demo (why session 3 had to stub it). Detector pinned to CPU — cheap next to the ViT-H pass and it dodges MPS RoIAlign/NMS gaps; an in-file # ponytail note marks the mobilenet swap if per-frame detection ever dominates on long videos.
• pyrender is dead headless on macOS (py_renderer forces PYOPENGL_PLATFORM=egl, no EGL on Mac; pyrender is even referenced in a type annotation, so a plain import-guard won't do). Centralized the permissive pyrender/OpenGL fake into .engine/HSMR/_headless.py — every entrypoint does import _headless before any lib.* import. QC still happens in Blender (fleet renderer + Lane C's tool); the runner dumps params.npz (SKEL poses/betas/cam_t — the Path-B payload) and mesh_qc.npz (verts/faces for Blender).
• chumpy failed to build → NOT a blocker (verified). The runtime SKELWrapper loads its pkls with plain pickle.load(encoding='latin1') — no chumpy import. chumpy only appears in SKEL's offline model-build script (merge_smplh_mano.py), which we never run. Ignore the WARN.

John's one step — drop the SKEL files (login + licence, so it's yours to do)

Register skel.is.tue.mpg.de → Download → "SKEL and BSM models" → skel_models_v1.1.zip (must be v1.1.1 — check changelog_v1.1.1.txt inside; older = silent incompatibility). Unzip, then:

mv /path/to/skel_models_v1.1 ~/Documents/MOCAPGOD/.engine/HSMR/data_inputs/body_models/skel

so that …/data_inputs/body_models/skel/skel_male.pkl exists.

Run the smoke test (once SKEL is in place)

cd ~/Documents/MOCAPGOD/.engine/HSMR && source .venv/bin/activate
PYTHONPATH=. python smoke_test.py -i data_inputs/demo/example_videos/gymnasts.mp4   # or .../example_imgs

Outputs → data_outputs/smoke/: params.npz (rotations), mesh_qc.npz (Blender QC), and console device/fps/NaN. Answers the Lane B smoke questions: MPS forward OK? timing (<2× realtime)? pose sane?

⚠️ HSMR is a per-frame recoverer → root is camera-space cam_t, not world-grounded. Fine for in-place DJ moves; locomotion (walk) needs Lane C's foot-contact root derivation or a grounding pass. This is the treaty's global-trajectory caveat, carried into Path B.