Pine Tree

A showcase piece, not an example, and the first in the nature category. It builds a procedural game-ready mature Scots pine, about 7.4 m tall with a broad, rounded crown about 8.7 × 7.3 m across, standing on a small disc of needle-litter soil:

• a trunk lathed in one piece from a five-lobed buttress flare, bedded in the soil mound, to a leader shoot. The tall bole is bare to about 3 m. It carries twelve deep vertical plate ridges that fade out between 1.9 m and 3.0 m into thin upper bark;
• five surface roots, one running out of each flare lobe and diving into the soil;
• five broken dead stubs and two long dead lower limbs, each limb carrying three dead twigs, on the bare bole;
• eight whorls of heavy limbs above the bole, 3 to 5 limbs per whorl. Each limb is a crooked, tapered bar that starts inside the trunk. Lower limbs are long, run out nearly level and carry bigger pads. Upper limbs rise more steeply and are shorter, which flattens the top. The crown is broadest across the hero view;
• one to three side twigs alternating along the outer part of each limb. Every limb and twig ends inside a needle clump, and so does the leader: 113 needle brushes overlap into one crown;
• clusters of two or three cones hanging under limbs in the upper crown;
• on the soil, five fallen cones, two mossy stones and two dead sticks.

Every draw comes from random.Random(SEED) in plan_tree(), before anything is built: whorl spacing, limb count, yaw, length, rise, droop, crook, cone clusters and the ground cover. Per-clump and per-tuft variety comes from a closed-form hash of indices. No flag draws from the stream, so a falsifier changes only what it names.

A needle clump is one closed shell: a brush of 108 long, thin needle strands. Its core is a small, dark, flattened cube-sphere (3 × 3 facets a side, 0.24 of the pad's radius), tipped up to 14° off level and lumpy. Every core facet is split in two, and each half is drawn out into one tapered strand. Each strand is aimed along the core's outward direction plus a hashed scatter, so the strands splay through the whole dome instead of lying in a plane, and it reaches 0.78–1.18 of the pad's ellipsoid. The core is small beside the strands' length, so every strand is a narrow sliver about ten times as long as it is wide. The underside of the ellipsoid is flatter than its dome. Strands are flat-shaded. A Tip point attribute runs each strand from a shaded base to a lighter, greyer point, and a second UV map (NeedleUV, not the baked UVMap) lays a fine line down each strand. Each clump takes its own soft blue-green tone: lighter outside and high, shaded in the crown's heart. Upward facets carry a glaucous bloom.

The strands are stylised, not botanical. A real Scots pine needle is 1–2 mm wide and 40–70 mm long. At that size the crown would need tens of thousands of strands, and the triangle budget holds about 12,000. Each strand here stands for a spray of needles: about 0.4–0.8 m long and a few centimetres wide at its base.

Two earlier passes were rejected. Lathed pads whose facets rose into pyramids read as crystalline shingles. Pom-poms whose wide core facets were drawn out into short points read as flat star rosettes, holly or maple leaves at thumbnail size. The small core and scattered aim fix both, at the cost of fewer, bigger clumps (113, down from 223).

The bark follows Scots pine: thick grey-brown plates on the lower bole, changing over 1.9 to 3.4 m into thin fox-red flaking bark. The upper bole and every limb are red. Wood, soil and stone are smooth-shaded, and every material boundary is a hard edge. Dead wood is barkless silver-grey. The soil is dark humus under crossing streaks of rust and grey needle litter, and the stones carry moss on their upward faces.

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 inline, not imported).

The collider is the convex hull of a 14-sided trunk alone, without ridges or roots, because players walk under the branches. The side count is chosen for the ceiling: a 20-sided hull measured 58 triangles and a 10-sided one 80, while 14 sides give 56.

Budgets#

Every budget is declared as a named constant. Every gate recomputes its value from the mesh, materials, UVs, evaluated LOD, collider, or export file.

DECIMATE COLLAPSE triangle counts are not identical across Blender series, so the LOD gate is a ratio band, not an exact count. Bake pixels are stochastic, so the bake gate is has_data plus operator FINISHED, not byte-identity. The plan is seeded and nothing else is random; two default runs print identical measurements.

Hygiene#

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

The soil disc's flat underside is the only geometry at Z = 0. The trunk's foot is bedded 0.10 m under the lowest soil round the flare instead of standing on the floor plane, and nothing is clamped to Z = 0, so no other face can land coplanar with it.

Branch seat, whorl tiers, plumb, clumps, ground and assembly#

These are the organic invariants. A tree has no joinery. What makes it read as a pine is that its limbs grow out of the trunk in whorls, its needles sit on the ends of its twigs, and it stands straight in the ground under its crown.

The trunk axis is read off the mesh. Every lathe ring shares one height, so the ring centroids give the axis and the ring radii give the girth. Each face carries a Part tag (trunk, limb, twig, clump, cone, soil and so on) so a shell can be named; every measurement is then made on the shell's geometry.

The clump seat is measured per clump against its own carrier, not against any bark nearby. The crown is dense enough that limbs pass through their neighbours' clumps, so "some bark is inside" would pass a clump whose own twig stops short of it.

Falsifiers#

Each falsifier violates one named budget. Every one was run on 5.2.1 and exited its declared code. The envelope was unchanged in every run.

--float-branches keeps each limb's path, so the tip and everything hung on it stay put. Only the tube's first ring moves out of the bark. --lean-crown bends only the bole under the lowest whorl and carries the crown over rigidly, so the envelope keeps its size to the tenth of a millimetre and the plumb budget is what fails. An earlier draft bent the whole axis quadratically, which grew the X extent 17.7 mm and exited 8 on the envelope instead; the bend was moved, the band was not widened. --bunch-whorls lifts one mid-crown whorl, whose limbs are not the extremes of the envelope. --short-twigs keeps the point count of every carrier, so the face budgets hold; it also splits the tree into 2 components, but the clump seat is checked first and names the cause. --float-litter likewise detaches the lifted pieces (9 components), and the bedding budget is checked before the component count. --drop-cones leaves the rest of the tree whole: 9 cones float free and the tree is the 10th component.

Run#

blender --background --python pine_tree.py --
blender --background --python pine_tree.py -- --skip-decimate
blender --background --python pine_tree.py -- --stray-vert
blender --background --python pine_tree.py -- --lift-z
blender --background --python pine_tree.py -- --float-branches
blender --background --python pine_tree.py -- --lean-crown
blender --background --python pine_tree.py -- --bunch-whorls
blender --background --python pine_tree.py -- --short-twigs
blender --background --python pine_tree.py -- --float-litter
blender --background --python pine_tree.py -- --drop-cones
blender --background --python pine_tree.py -- --output pine.png

Smoke passes no flags.

The hero keeps the tree at HERO_YAW_DEG (0°) and looks at it from the front left, across the crown's broad axis. The camera sits a little below the crown's middle, so the skirt of heavy lower limbs reads against the wall with the red limbs showing through, and the bare bole, dead limbs and soil disc read below it. Framing measures fill x 0.509, y 0.794. A warm wedge pools on the floor behind and to the right and washes the wall above it.

Exit codes#

File-local. 9 is a valid check code. 10 is reserved for gallery_framing.check_framing on the --output path. 15–17 and 19 are the hygiene, joint-fit and plumb family. 18 is not used: no budget here is a wrapper's seat. 20–23 are file-local; 22 and 23 are checked before 21, so a falsifier that also detaches parts still names its own budget. 24 is the asset-quality floor on the render path: check_asset_quality returns 11, which this piece already spends on the collider ceiling, so the call site remaps it.