Seed-deterministic, baked at spawn, emitted straight into the 24-byte packed
vertex format. Two devices given the same seed produce byte-identical
geometry — which is what lets a forest replicate as (preset, seed, position)
tuples instead of mesh data.
- L-system plants: expansion + 3D turtle + skeleton, 8 species (oak, pine,
palm, bush, fern, cactus, dead, grass)
- Surface nets (not marching cubes — fewer, better-shaped triangles at
low-poly) for rocks, boulders, mushrooms, clouds, blobs
- Spline tracks with width, banking, curbs and rails, returning centreline
frames that carry lap distance — so spawn points and checkpoints derive
from the track instead of a second hand-written list
- Poisson-disk scatter with flatness/height rules
- Texture generator with CPU mip chains (backends never generate them)
- LRU cache keyed by FNV-1a over the full recipe with floats hashed by exact
bits; -0.0 and 0.0 normalise together (identical geometry), 4.0 and
4.000001 stay distinct. Meshes hand out as Rc so eviction cannot pull
geometry out from under a frame mid-draw
- DrawGameFoliage: growth and wind as an OPT-IN shader variant, a sibling of
DrawGameSkinned rather than a flag inside the shared shaders — wind costs
~20 vertex ALU and the cube shader draws most of the world. Growth and flex
weights share one packed nibble pair, so both animations cost zero extra
vertex bytes
A realistic forest — 150x150 m, 582 trees, 3 species, 6 seeds — generates in
1.70 ms with 470 KB resident: 6 generations and 576 cache hits.
Three bugs the unit tests had passed, found by writing an ASCII silhouette
probe because captures were out of scope: every species came out ~4x its
requested height (the test compared two sizes RELATIVELY, so a uniform
overshoot sailed through — now the finished skeleton is measured and rescaled,
and the test asserts absolute height for all 8 species at three sizes); palm
emitted no foliage at all because its L-system contained no leaf symbol; and
cactus sprawled sideways like a shrub. Pine also dropped from 4 iterations to
3 — 15032 -> 2504 triangles, 728 -> 68 us — because 15k triangles for one
background tree is indefensible.
Honest caveat: that is a silhouette judgement, not a rendered one. Shading,
leaf-card orientation and the wind/growth animation are visually unverified.
Script verbs are not wired yet — the crate is a library only.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
