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.

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.

Joint fit and seat#

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).

Fire, char and soot (render and shaders only; no budget changed). The logs were a clean bark brown and the ring a pale concrete grey, so nothing in the still said the fire had ever been lit. A heat field (distance from a core just above the ash bed) now drives three things in the shared shaders: wood chars to near-black toward the flames, the hottest charred wood shows cracked embers (a Voronoi edge network, masked by a coarse noise so only some cracks are live), and stones are smoke-blackened where they face the fire. Stone base colours dropped to a warm dark fieldstone with a wider per-stone tone spread. The render adds a warm point light in the ember bed. Material slots and face counts are unchanged.

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.

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.