signpost

Signpost

A showcase piece, not an example. Procedural timber fingerboard signpost (square post, pyramidal cap from the post half plus overhang, two axis-aligned painted boards with wedges cut from the board section, iron shoe collar and U-wrap straps) then the shipped pipeline: unique-cell UVs, Cycles high-to-low normal bake, LOD chain, convex collider, Unity glTF export.

Boards are yaw 0. Finger tips are wedges whose base is the board's own thickness×height, bitten into the board so the base face is inside it. The cap is added after the post bevel. The post stays on the origin. Hygiene family 15–19: --stray-vert, --lift-z / --short-shoe, --gap-board, --float-strap, --yaw-boards.

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). Hygiene combinatorics match examples/mesh-hygiene-audit (copied, not imported).

Intended size: 1.48 m post, boards 0.62 m and 0.54 m, 0.118 m post stock; outer AABB 1.260 × 0.142 × 1.551 m.

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	320–480	376 / 376 / 376
LOD1 ratio	0.32–0.62 of base	0.5000 / 0.5000 / 0.4681
LOD2 ratio	0.10–0.35 of base	0.2181 / 0.2181 / 0.1649
Materials	exactly 3 distinct, ≥24 metal, ≥12 board, ≥12 wood	3 slots, 108 metal, 22 board, 60 wood
UVs	in 0..1, AABB overlap ≤ 1e-5	in range, overlap 0
Outer AABB	(1.260, 0.142, 1.551) m ± 0.015	(1.2600, 0.1420, 1.5510), zmin 0
Collider tris	≤ 180	52
Export	written, size > 0	35648 / 35648 / 35640 bytes

Base triangles dropped from 504 to 376 in the quality pass: glued diamond cubes and a solid shoe block became wedges and a four-plate collar. Outer AABB tightened from 1.368 × 0.201 × 1.566 m.

DECIMATE COLLAPSE triangle counts are not identical across series — 5.2.1 is leaner on LOD1 and LOD2. 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 is closed-form; the only RNG is the seeded per-piece wood tone. Bevel inputs are sorted by edge index, so the face order is the same on every run. Export byte counts differ on 5.2.1 (glTF serializer), not a gated axis.

Surface and stage

The quality pass found no geometric defect: the boards, straps, bands and shoe seat as their budgets say. The defects were surface. The finger boards were flat pale yellow; they are now cream paint worn through to the wood by a noise mask, a shade apart per board. The iron read as chrome (metallic 1.0, roughness 0.38) and is now rusted. The post has its own tone and grain. The stage grid grew from 14 to 60 m, because the wall's left edge showed in the corner of the hero. The temp .glb is removed after its size is measured. With no new geometric defect, there is no new budget.

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 shoe plates	≥1, each zmin ≤ 0.002	4, 0.00000

Joint fit and orthogonal boards

Axis	Declared	Measured (all three)
Board-to-post BVH gap	≤ 0.008 m	0.00500
Strap-to-post BVH gap	≤ 0.008 m	0.00300
Board AABB Y (axis-aligned)	≤ 0.055 m	0.0280

Falsifiers

Each violates one named budget. All 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-shoe	named shoes plant at z=0	16
--gap-board	board-to-post BVH gap	17
--float-strap	strap-to-post BVH gap	18
--yaw-boards	board AABB Y (orthogonal)	19

--short-shoe lifts only the iron shoe plates. After zmin snap the post is the AABB zmin, so the AABB gate would still pass; the named shoe stations fail. --gap-board moves the board inner station outside the post. --float-strap adds Y offset to the U-wrap so it no longer bites. --yaw-boards restores a 0.12 rad yaw; the AABB secondary extent exceeds the thickness bound.

Run

blender --background --python signpost.py --
blender --background --python signpost.py -- --skip-decimate
blender --background --python signpost.py -- --stray-vert
blender --background --python signpost.py -- --lift-z
blender --background --python signpost.py -- --short-shoe
blender --background --python signpost.py -- --gap-board
blender --background --python signpost.py -- --float-strap
blender --background --python signpost.py -- --yaw-boards
blender --background --python signpost.py -- --output signpost.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 ≠ 3 distinct slots, or wood/board/metal faces missing
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	Hygiene (--stray-vert lands here)
16	Grounded zmin / named shoes (--lift-z, --short-shoe)
17	Board-to-post gap (--gap-board)
18	Strap-to-post gap (--float-strap)
19	Board yaw / AABB Y (--yaw-boards)