derive_chunk_context now derives channel_anchor_m and coast_anchor_m from
the Region-or-higher seed path (D-239 §10); all five voxel placement sites
measure distance to these anchors in continuous world coordinates:
- T-1040: compute_channel_state / compute_meander_reach_channel /
in_levee_band subtract the region anchor instead of measuring from the
world origin axis — active channels now exist in their chunks anywhere
on the body, continuous across chunk boundaries. has_active_channel is
honest in both directions (band-crossing gate; floor covers the
BraidedDelta belt at short wavelengths).
- T-1041: fjord/cliff/gorge/delta drop their rem_euclid(64) chunk-frame
folds — one valley/coastline/fan per region instead of one per chunk.
D-239 §9 chokepoint widths preserved; two i32 wall-rise overflows on
region-scale distances fixed by clamping before multiply.
Harness: 6 new believability tests (channel presence + gate honesty at
chunk (1000,-750), cross-boundary continuity, one-landform-per-region,
braid-belt confinement); drainage sweeps strengthened with anchor-band
chunks. Voxel golden regenerated deliberately: case A now pins a genuinely
in-channel Shallow voxel on the anchor, case C a Deep trough voxel
matching its label; case B byte-identical and L0/L1 cascade golden
untouched (no upstream leak). Review: approved, three minors addressed
(truncation-convention docs, delta gate floor, case C relocation).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
D-239 §1/§7/§10 — the lower derivation chain end-to-end with the AlluvialPlain
fallback only (specialized families are T-1029).
- chunk_context.rs: ChunkContext (64m) — basin_direction + meander phase/wavelength
+ active-channel params. NO per-tile flow_direction[64x64] (D8 ~152m coarser than
a chunk, D-239 §10); features >64m seed from Region-or-higher. SeedDomain::ChunkContext=8.
- voxel.rs: VoxelColumn (1m) composing the D-228 tile axes (TerrainMaterial /
FloorMaterial=None / Vegetation / Water / elevation_m). Derive-on-demand + VoxelCache
(LRU BTreeMap, never persisted per D-227). Domain warp (T-1026) wired through:
f64 warp -> as-i32 truncation to the voxel address; all material/morphology gates
integer (D-010 — the meander wavelength f64 is truncated before the Water decision).
- AlluvialPlain generator: Soil/Wetland terrain, climate vegetation, integer-meander
channel (Shallow/Deep) from ChunkContext. The other 7 families are dispatch stubs
(canonical terrain material, fall back to AlluvialPlain geometry) — no panic.
29 new tests incl end-to-end determinism (same seed/pos -> identical column),
cache hit/miss/eviction/re-derivation, warp-applied. cargo test 1563 pass,
clippy -D warnings clean, fmt clean.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
jpmschweitzerandClaude Fable 5