Task 17's hard 1.2 x CraterRadius cutoff left a visible un-eroded disc with a hard
edge. Measured (radius dump, seed 1280587109): the carve writes only inside 0.80 x
(640 px) and its displacement is EXACTLY 0 beyond that, so the 640-960 px annulus
was 620,811 LAND cells of ordinary terrain held smooth for no geometric reason.
That annulus is now eroded — 98% of those cells are touched.
The protected core is the carve's own extent (CraterErosionCore, 0.80 x).
CraterErosionMode selects the transition: "full" applies full strength at the core
boundary (older-crater look), "feather" ramps 0->full out to CraterErosionFeather
(1.05 x, mirroring the detail pass) for a younger-crater look with no seam.
Implemented as a WEIGHT that scales carve and deposit amounts, not a skip, which is
what makes feather a one-liner. Default "feather" pending the gate.
Core = the carve radius is load-bearing, not tidy: the carve runs AFTER erosion and
scales height toward the sea target, so it amplifies any erosion delta inside its
radius. Measured at a 0.50 core: 79 cells newly below the rendered sea and 113,310
below-sea cells disturbed — the in-pass flood guard cannot see this because it
measures before the carve. At 0.80 the two passes touch disjoint cells and the
guarantee is exact again (0/0/0). A narrower core also reclaims nothing extra, since
the over-protected annulus lies entirely outside the carve. MapGenerator now owns
CRATER_CARVE_FACTOR as the single source of that 0.80 and warns loudly if the
configured core is narrower.
Verified both modes, seed 1280587109: 1_biomes/0_water md5-identical to erosion-OFF,
BIOM/WBID bitwise equal, 0 newly below/above sea, 0 below-sea cells modified, 0
cells modified inside the core, island top 457.65 m unchanged, isotropy 1.005/1.007.
Bay-to-ocean connection demonstrated explicitly by flood fill through rendered
water to the map's north border (2,122,935 cells), not merely argued from the sea
clamp.
EROS body version -> 3: craterExclFactor replaced by craterCoreFactor +
craterFeatherFactor + craterMode. Round-trip harness PASS with a real v3 payload.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Deposition now spreads over the same cone brush as carving, and the per-cell
erosion ledger becomes a signed NET displacement ledger, so both caps are
measured from the height the pass found. Brush-spreading alone cut the spike
15.49 -> 6.12 m at task-17 dials, but NOT at hierarchy dials (long paths carry
far more sediment; a loaded droplet meeting a rise dumps min(rise, load) at
once -> 25.5 m). So deposition also gets governor 4, ErosionDepositCap
(default 6 m, <= 0 = unbounded), asserted on exit like the carve cap.
Dial defaults retuned for a drainage HIERARCHY: 250k droplets x 384 steps at
inertia 0.35 / evaporation 0.004, erode 0.12, carve cap 15 m. Diagnosis was
that lifetime 48 let a droplet travel at most 48 px on a ~3000 px island
radius, so paths could not overlap into trunks: the deepest task-17 features
were 43x36 px patches. Now 177 channel systems of 200+ cells at the 3 m
threshold, top one 204x279 px with 14 tributary tips; cells past 5 m up 8.6x
(4,948 -> 42,385) while the fine rills are retained. Verified descending, not
contour-locked: 0/155 components have drop/extent < 0.12 (median 1.13).
EROS body version -> 2 (deposit cap inserted after the carve cap); v1 payloads
are skipped whole by the existing rule. HydraulicErosion.VERSION now reads
BlueprintFormat.EROS_VERSION instead of restating it — the local copy had
already drifted and stamped a v2 body as v1, which readers decode with every
float shifted by one field.
Oracle green on both seeds (1280587109, 1512575962): 1_biomes/0_water
md5-identical erosion-ON vs OFF, BIOM/WBID bitwise equal. Flood guard 0 new
water px, 0 below-sea cells touched, crater zone untouched, island top
unchanged, carve field isotropic to 1.4% across the folded 45deg period.
Erosion pass 34 s at these dials.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Erosion: "off"|"v1" gate (default off, pending the developer's gate). Output-only:
applied to the render map after detail, before the crater carve; the classify path
reads pre-erosion heights, so biomes/water stay byte-identical (verified: OFF run
bit-identical to the task-14 reference; ON run BIOM/WBID identical to OFF).
Governors: droplet count / lifetime / per-cell carve cap (ledger-enforced, thrown
on violation). Sea clamp: below-sea cells read-only, land never carved below
sea+margin — rendered coastline provably fixed (asserted per generation). Crater
excluded at 1.2×R. Deterministic from resolvedSeed+9271 (PCG32). New EROS
blueprint section (writer/parser/harness/format doc). Supersedes the reverted D8
approach with the organic droplet model.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
