destroyulator/LANES/LANE2-asset-pipeline-fracture.md

LANE 2 — Asset pipeline: cell-fracture stage + Destroyulator prop batch

Owns: ~/Documents/meshgod (SEPARATE repo — not the destroyulator monorepo). For: an Opus 4.8 session. Runs on: M3 Ultra; Blender at /Applications/Blender.app.

Objective

Give the meshgod factory a fracture stage so props arrive pre-shattered for smashing, then batch-generate Destroyulator's workplace props and push them to 3GOD. This upgrades Lanes 1 & 3 from "single-box smashable" to real shard-by-shard destruction.

What already exists (read first)

• meshgod/finish.py + scripts/finish_glb.py — the headless-Blender subprocess pattern to copy: launches /Applications/Blender.app --background --python <script> -- <args>, parses a FINISH_RESULT:{json} line from stdout. Finishing does join→solidify (watertight!) →decimate→brighten→normalize→export GLB.
• meshgod/batch.py — resumable manifest runner (python3 -m meshgod.batch manifest <f.json> --out <dir>, content-hashed IDs, checkpoints, --workers).
• meshgod/pipeline.py, config.py — the OpenRouter→fal.ai→finish flow. Cost is real (~$0.10–0.55/asset); fal key in gitignored open.txt. Check remaining credit before a big batch.
• 3GOD push: MESHGOD/scripts/test_3god_push.py (on M1) guards the depot auth/slug contract; find/mirror the actual push helper meshgod uses to POST a finished GLB to digalot.fyi/3god.

Deliverables

1. meshgod/scripts/fracture_glb.py — headless Blender cell-fracture

Mirror finish_glb.py's structure exactly (arg parsing, FRACTURE_RESULT:{json} stdout line).

• Input: a finished watertight GLB + --chunks N (default 12) + --out <path>.
• Enable the Cell Fracture addon (bpy.ops.preferences.addon_enable(module="object_fracture_cell")) and run bpy.ops.object.add_fracture_cell_objects(source_limit=N, ...) on the imported mesh. (Blender 5.1 — verify the addon module name; if renamed/removed, fall back to a Voronoi geometry-nodes or boolean-based split, but Cell Fracture is preferred.)
• Each chunk: recenter its origin to its own bounds center (so it can become a rigid body), keep the parent's material.
• Export all chunks as a single <name>.fractured.glb whose root's direct children are the chunk meshes named chunk_00…chunk_NN (SHARED-CONTRACT #2 in PLAN.md). Report chunk count + whether any chunk is non-manifold.

2. meshgod/fracture.py (module) + CLI

python3 -m meshgod.fracture <in.glb> --chunks 12 --out <out.fractured.glb> — thin wrapper that subprocess-launches the script (same pattern as finish.py). Optionally add a --fracture flag to batch.py so a manifest entry can request "fracture": {"chunks": 12} and get both <name>.glb + <name>.fractured.glb out.

3. meshgod/manifests/destroyulator.json — the prop batch

Workplace hero props, real-metre height_m + tri budgets. Include at least: office printer (the boss!), office desk, monitor/CRT, desk phone, filing cabinet, water cooler, office chair, ceiling fluorescent light, coffee mug, potted plant, wall clock, cardboard box; record-store extras: turntable, amp/speaker, cash register, wall shelf. Each entry: {name, prompt, height_m, tris, fracture:{chunks}}. ~16 assets ≈ $3–8, ~30 min. Confirm the fal budget covers it before running; if low, do the top 6 first.

4. Push finished + fractured GLBs to 3GOD

Use meshgod's existing depot-push path. Land both the intact and .fractured.glb on the digalot.fyi/3god shelf so Lanes 1 & 3 can pull them by slug.

Acceptance

• fracture_glb.py on one finished GLB (e.g. outputs/robot_game.glb) yields a .fractured.glb with ≥8 chunk children named chunk_*; verify by loading it in Blender headless and printing child count + names.
• The manifest runs (or a 2-asset subset does) end-to-end: intact + fractured GLBs on disk, watertight, correct scale, pushed to 3GOD (GET /api/list shows the new slugs).

Gotchas

• Cell Fracture needs the mesh to be a single manifold object; run it AFTER finish's solidify.
• fal costs money per asset and the key is shared/rotating — read open.txt, don't hardcode, and cap batch size to the remaining credit.
• Keep chunk counts modest (8–16). Hundreds of chunks tank the consuming physics engines.

Definition of done

Fracture stage works and is documented; destroyulator.json (or its top-6 subset) generated, finished, fractured, and pushed to 3GOD; committed + pushed to meshgod's own remote. Post the list of produced slugs so Lanes 1 & 3 can consume them.