campfire

Campfire

A showcase piece, not an example. Procedural campfire (two-course running-bond ring of 14 rounded fieldstones per course, pit-floor cobbles, ash with embers, a kissing log tripod that overshoots a shared apex ring, floor logs, and charcoal) then the shipped pipeline: unique-cell UVs, Cycles high-to-low normal bake, LOD chain, convex collider, Unity glTF export.

Courses share a Z plane; --gap-courses is the falsifier. Teepee axes aim at a ring of radius (STICK_R * 0.55) / sin(π/N) and overshoot so the caps cross; --float-logs inflates that ring.

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	1400–3600	2760 / 2760 / 2760
LOD1 ratio	0.32–0.62 of base	0.5000 / 0.5000 / 0.4993
LOD2 ratio	0.10–0.35 of base	0.2196 / 0.2196 / 0.2196
Materials	exactly 3 distinct; ≥80 wood, ≥24 ash, ≥200 stone	3 slots; 216 / 48 / 1416
UVs	in 0..1, AABB overlap ≤ 1e-5	in range, overlap 0
Outer AABB	(0.807, 0.808, 0.404) m ± 0.015	(0.8024, 0.8022, 0.4037), zmin 0
Collider tris	≤ 360	162
Export	written, size > 0	231952 / 231952 / 231944 bytes

Base triangles dropped from 3616 to 2200 in the quality pass: the old piece stacked identical boxes with a mortar gap and a teepee that met at one point. The rebuild is two seated courses plus crossing sticks; hidden overlapping volume went away. The second pass took it to 2760: each stone is now a lofted, chamfered lump instead of a four-sided wedge.

DECIMATE COLLAPSE triangle counts are not guaranteed 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. Stone-width jitter uses fixed seed 17; each stone's shape draws from its own seeded generator. glTF byte size differs on 5.2.1.

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: 14 bottom stones	each zmin ≤ 0.001	14, stone_z 0.00000
Ring plan	0.807 m dia × 0.176 m high ± 0.04	0.8023 × 0.1759
Stone variation (exit 20)	per course, spread of stone outer radius, and of crown height on the top course, each ≥ 0.006 m	0.01269 (smallest spread)

Joint fit and seat

Axis	Declared	Measured (all three)
Teepee kiss (BVH nearest at caps)	≤ 0.008 m	0.00034
Course seat (upper zmin − lower zmax)	abs ≤ 0.004 m	0.00000

Stones, wood and ash

The ring was 28 identical curved bricks: flat tops, flat faces, one height, one grey. It read as a concrete kerb. Each stone is now a chamfered octagon section lofted along its span, swelling to a seeded belly mid-stone and pinched and capped at the ends, with a seeded radial offset and outer-face wobble. Top-course stones get a seeded domed crown. The beds stay flat, and the bottom course's crown stays at the bed height, so the upper course still seats (course seat 0.00000). The stated ring height rose from 0.156 to 0.176 m for the crowns.

Stone variation asserts the ring is not one stone repeated. --uniform-stones gives every stone the same draw — each jitter at its upper bound, so the ring keeps the envelope of its widest seeded stone and only this budget fails (exit 20, spread 0.00000).

Stone is isotropic mottling, speckle and pitting with a seeded tone per stone (stone-archway's recipe, reading PieceTone); sticks and logs carry their own tone and grain along their axis; the ash has sparse ember glow. 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-stones	named bottom-course supports at Z=0	16
--float-logs	teepee kiss	17
--gap-courses	course seat	18
--uniform-stones	stone variation	20

Run

blender --background --python campfire.py --
blender --background --python campfire.py -- --skip-decimate
blender --background --python campfire.py -- --stray-vert
blender --background --python campfire.py -- --lift-z
blender --background --python campfire.py -- --short-stones
blender --background --python campfire.py -- --float-logs
blender --background --python campfire.py -- --gap-courses
blender --background --python campfire.py -- --uniform-stones
blender --background --python campfire.py -- --output campfire.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; 20 is file-local.

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 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 bottom stone floats
17	Joint fit: teepee kiss (--float-logs)
18	Seat: course gap (--gap-courses)
19	Ring diameter or height off the stated real-world size
20	Stone variation: the ring stones are identical (--uniform-stones)