usd_models/scripts/usd_cleaner/Readme.md

USD models cleaner

Finds the USD models under assets/usd_models that no scene actually uses, and deletes them. Pure standard library — no Isaac Sim, no pxr, no pip installs.

Two scripts, run in order:

File	What it does
usd_models_cleaner.py	Seeds from assets/scenes/*.json, follows references inside the USD files transitively, writes the list to JSON. Read-only.
usd_models_delete.py	Takes that JSON and deletes the listed files, then removes folders left without any USD. Destructive.

Both resolve paths against the repo root, so they work from any directory.

1. Build the list

python3 scripts/usd_cleaner/usd_models_cleaner.py --unused

Writes unused_usds.json next to the script — every USD file under assets/usd_models that no scene references. That is the delete list.

Without --unused it writes used_usds.json instead: the models that are referenced. Useful as a sanity check.

Flag	Effect
--unused	Invert: list what is NOT reachable (the delete list)
--aggressive	Drop the sibling-directory guard (riskier, deletes more)
--no_follow	Scene JSONs only — unsafe, reproduces the old broken behaviour
--out PATH	Write somewhere else (a bare name lands in this folder)
--no_out	Print only, write no file
--verbose	Annotate each path with the scenes referencing it
--scenes_dir / --models_dir	Point at different directories

2. Preview

python3 scripts/usd_cleaner/usd_models_delete.py unused_usds.json --dry-run

Prints every file and folder that would go, plus the total freed. Touches nothing. Always run this first.

3. Delete

python3 scripts/usd_cleaner/usd_models_delete.py unused_usds.json

Prints a summary and asks [y/N] before removing anything.

Flag	Effect
--dry-run	Preview only
--yes	Skip the confirmation prompt
--keep_empty_dirs	Delete the files but leave USD-less folders in place
--models_dir	Confine deletion to a different directory

Rules it follows

• Folder removal. A folder is removed only if it held a USD file and now holds none. A folder that never held one — textures/, material/ — belongs to its parent model and is left alone, so surviving models keep their assets.
• Protected folders. .git, .svn, .hg, __pycache__ and any dotted folder are never swept. Without this the "no USD inside" rule would delete assets/usd_models/.git wholesale.
• Containment. Deletion cannot leave --models_dir. A ../ in the list aborts the run instead of escaping.
• Only .usd, .usda, .usdc, .usdz count as models. A .png or a backup file whose name contains .usd is not a model and is not counted.

How references are followed

A scene names a wrapper; the geometry and joints usually live elsewhere. The cleaner therefore starts at the scene paths and walks outward:

1. .usda text — parsed for @asset/path@ (and the @@@path@@@ form), resolved relative to the file holding the reference. Reliable.
2. .usdc binary — the token table is compressed, so printable strings are mined and kept only when they resolve to a file that exists. Best-effort.
3. Companion folder — X.usd beside a folder X/ pulls in that whole folder. This is the convention these assets use and it is what catches what the binary scan misses.
4. Sibling directories — a reachable binary USD also protects the directories next to it, since its real references are unreadable. kitchen_background.usd keeps localized/ this way. --aggressive turns this off.

Every step is repeated transitively until nothing new is reached.

Why this matters

An earlier version scanned scene JSONs only. It deleted model_dishwasher_v2/resource/v_0/link_default_0.usda — never named by any scene, but the file holding the dishwasher's articulation. Isaac Sim then failed with:

RuntimeError: Failed to find an articulation when resolving
'/World/envs/env_0/model_dishwasher'

--no_follow reproduces that behaviour for comparison. Do not delete with it.

Before you delete

The binary side is a heuristic, not a parser. Only pxr (via /isaac-sim/python.sh) can resolve .usdc references with certainty. Treat the list as a strong suggestion, not proof.

Scene JSONs may also not be the only referrer — task configs or code can name a model directly.

assets/usd_models is a git repo, which is the real safety net: after deleting, git status shows every removal and git reset --hard HEAD restores them. Load a scene before committing the deletions.

Current numbers

158 paths declared by scenes expand to 264 reachable USD files; 652 are unreachable. Scene-JSON-only scanning would have kept just 158 and deleted 729 — the 106-file difference is what broke the dishwasher.