anvil

Anvil

A showcase piece, not an example. Procedural London-pattern anvil on a coopered timber stump (16 jittered staves, chord-lofted iron hoops, a sawn head, spreading foot, pinched waist, one slotted face with hardy and pritchel through-holes, oval-lofted horn) then the shipped pipeline: unique-cell UVs, Cycles high-to-low normal bake, LOD chain, convex collider, Unity glTF export.

The face is one add_slotted_slab so hardy/pritchel are real holes in a single shell, not nubs glued onto stacked boxes. Hoops evaluate the same host_outer_r chord as the stave flats. --round-band is the falsifier: a circle of radius_at(z) instead of the chord.

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.

Axis	Declared	Measured (4.5.11 / 5.1.2 / 5.2.1)
Base triangles	2500–4500	3052 / 3052 / 3052
LOD1 ratio	0.32–0.62 of base	0.5000 / 0.5000 / 0.5000
LOD2 ratio	0.10–0.35 of base	0.2195 / 0.2195 / 0.2195
Materials	exactly 2 distinct; ≥400 wood, ≥400 metal faces	2 slots; 1040 / 854
UVs	in 0..1, AABB overlap ≤ 1e-5	in range, overlap 0
Outer AABB	(0.621, 0.414, 0.489) m ± 0.015	(0.6210, 0.4137, 0.4890), zmin 0
Collider tris	≤ 280	134
Export	written, size > 0	248532 / 248532 / 248516 bytes

Base triangles dropped from 6616 to 2988 in the quality pass: overlapping face boxes and a beveled superellipse horn became one slotted slab plus a circular oval loft. Hidden coincident faces were the waste.

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. Stave-width jitter uses fixed seed 17, and the per-piece wood tone its own seed. Export byte counts differ on 5.2.1 (glTF serializer), not a gated axis.

Hygiene

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

Axis	Declared	Measured (all three)
Non-manifold edges	0	0
Loose verts / edges	0 / 0	0 / 0
Doubles merged at 1e-5	0	0
Zero-area faces	0	0
N-gons	0	0
Coplanar disjoint face pairs	0	0
Grounded: zmin	within 1e-4 of 0	0.0000
Named supports: 16 staves	each zmin ≤ 0.001	16, stave_z 0.00000
Body plan	0.621 m long × 0.180 m high ± 0.05	0.6210 × 0.1800
Waist form	corner reach at the pinch ≥ 0.80 (an ellipse is 0.707)	0.8572

Joint fit and seat

Axis	Declared	Measured (all three)
Foot-on-head BVH gap	≤ 0.006 m	0.00300
Hoop bite (host r − inner hoop r)	0.0012–0.008 m	0.00300

Waist, steel and stump

The waist was lofted from ellipses, so under the rectangular face it read as a turned funnel, not a forged anvil. It is now a superellipse section (exponent 4.5) through five stations that flare from the foot in to a pinch and out to the body. Waist form measures corner reach at the narrowest ring: how far a section vertex fills its bounding rectangle's corner. --round-waist restores the ellipse and exits 19 (0.7071).

The steel was satin (metallic 0.92, roughness 0.32) and read as chrome; it is now dark forged steel with rust. Staves and head carry their own wood tone and grain. The stage grid grew from 14 to 60 m. The temp .glb is removed after its size is measured.

Falsifiers

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

Flag	Budget violated	Exit
--skip-decimate	LOD1 ratio band	9
--stray-vert	loose vertex count is 0	15
--lift-z	bounding box zmin is 0	16
--short-staves	named stave supports at Z=0	16
--float-anvil	foot-on-head gap	17
--round-band	hoop bite band	18
--round-waist	waist form	19

Run

blender --background --python anvil.py --
blender --background --python anvil.py -- --skip-decimate
blender --background --python anvil.py -- --stray-vert
blender --background --python anvil.py -- --lift-z
blender --background --python anvil.py -- --short-staves
blender --background --python anvil.py -- --float-anvil
blender --background --python anvil.py -- --round-band
blender --background --python anvil.py -- --round-waist
blender --background --python anvil.py -- --output anvil.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.

Code	Meaning
0	Success
1	Uncaught exception (FATAL wrapper)
2	argparse / usage
3	Mesh did not build / no UV layer
4	Base triangle count outside range
5	Material count ≠ 2 distinct slots, or a face-count floor missed
6	UVs outside 0..1
7	UV AABB overlap above tolerance
8	World AABB off declared outer size
9	LOD ratio band (--skip-decimate lands here)
10	Framing gate (render path only)
11	Collider triangle count above ceiling
12	Bake did not finish or image has no data
13	Export file missing or empty
14	--output produced no file
15	Mesh hygiene: loose, non-manifold, zero-area, doubles, n-gons, z-fight
16	Not grounded: bounding box zmin off 0, or a named stave floats
17	Joint fit: foot-on-head gap (--float-anvil)
18	Seat: hoop bite band (--round-band)
19	Body length or height off the stated real-world size, or waist form (--round-waist)