Treasure Chest

A showcase piece, not an example. Procedural iron-bound chest (slatted hollow body, barrel-vault lid, U-wrap bands, corner irons, lock plate, hinge barrels with lid knuckles, wooden feet) then the shipped pipeline: unique-cell UVs, Cycles high-to-low normal bake, LOD chain, convex collider, Unity glTF export.

The lid is one lofted vault slab, not stacked boxes. Hinge join is measured from local lid knuckles over the barrels — a spanning stile only has verts at the X ends, 8 cm from the knuckles, and reports a false gap.

It asserts budget conformance of the generated result. It does not witness an API contract. "It rendered without error" is not a check.

Composes skills mesh-editing-and-bmesh, bake-high-to-low, depsgraph-and-evaluated-data, engine-export-presets, and snippets bake_normal_high_to_low.py, setup_bake_target_image.py, lod_chain.py / decimate_to_budget.py, convex_hull_collider.py, export_preset_unity.py (helpers copied, not imported as a package).

Budgets#

Declared as named constants; every gate recomputes from the mesh, materials, UVs, evaluated LOD, collider, or export file.

Hygiene#

Recomputed from the generated mesh, not asserted about the script.

Joint fit and seat#

DECIMATE COLLAPSE triangle counts are not identical across series — the gate is a ratio band, not an exact count. Bake pixels are stochastic; the gate is has_data plus operator FINISHED, not byte-identity. Construction uses no RNG. Export byte counts may differ by a few bytes across series.

Lid bands#

Found on the inspection sheet: the three iron bands on the vaulted lid were each eight boxes rotated about X by +t, with t the arc angle at the segment. At angle t the arc's tangent in (y, z) is (cos t, -sin t), which is a rotation of -t. Every segment sat 2t off the tangent, and in the side orthos the bands fanned out from the lid like feathers. The same sign error tilted the front-edge band caps and the hasp. Those segment tips also set the Y envelope: the bounding box shrank 18 mm when they were fixed, so the declared outer size was re-fitted to (0.764, 0.524, 0.696).

Each band is now one add_arc_slab on the lid's own vault: the same angular span and segment count as the lid timber, inner radius LID_BAND_BITE inside the lid, outer radius BAND_T beyond. Caps and hasp rotate by -t. lid_band_audit un-rotates the lid about its hinge, takes each lid-iron shell's radius from the vault axis, counts the shells spanning at least 60% of the arc, and requires every band vertex inside the band's radial range (exit 18). The builder re-centres the whole mesh after swinging the lid, so the audit recovers that shift from the feet, which are symmetric. The rest of the low body is not: the hasp hangs from the lid down the front. --lift-lid-bands floats the bands 5 mm off the vault (measured 5.000 mm) while the envelope stays inside tolerance.

The timber gets the per-plank tone and grain shader, and the iron gets rust wear (copied from shipping-crate). The temp glTF export is removed after it is measured.

Falsifiers#

Each violates one named budget. All eight were run on 4.5.11, 5.1.2 and 5.2.1 and returned the same code on each.

Run#

blender --background --python treasure_chest.py --
blender --background --python treasure_chest.py -- --skip-decimate
blender --background --python treasure_chest.py -- --stray-vert
blender --background --python treasure_chest.py -- --lift-z
blender --background --python treasure_chest.py -- --short-legs
blender --background --python treasure_chest.py -- --float-hinge
blender --background --python treasure_chest.py -- --narrow-bands
blender --background --python treasure_chest.py -- --lift-lid-bands
blender --background --python treasure_chest.py -- --output chest.png

Smoke passes no flags.

Exit codes#

File-local. 9 is a valid check code. 10 is reserved for gallery_framing.check_framing on the --output path. 15–19 are the hygiene and joint-fit family.