Two surgical refinements of rivers/03b's fix 3. Everything else (confluence,
the rim cap, the faithful default) unchanged. Courses only: no height mutated,
no water filled or created — asserted per seed by a raw-bit digest.
- FIX A (ISLA_LAKE_PREFER_RATIO, default 0.4): a dry-basin router goes to the SEA
unless cost_lake < ratio * cost_ocean, i.e. unless a lake is materially cheaper.
rivers/03b used "nearest of {ocean, lake}", which is exactly ratio < 1.0 and
captured 12 rivers, halving the sea mouths. Both leg costs are now recorded for
every router so the knob is readable off the table without a re-run.
- FIX B (OwnBasinLakeEnder): a natural lake-ender terminates at the water inside
its OWN terminal basin at any size. The 20,000 px significance threshold had
exiled 999999937 #3 from its sub-threshold home lake, sending it ~5,800 px along
the shoreline. The threshold still applies to routers choosing a distant lake.
As predicted, the rim cap re-arms: 31415926 #2 (66.7 m) now goes to the sea and
is refused, rather than being hidden in a lake.
Both fixes are off by default, so faithful mode still reproduces rivers/03 and
refined mode still reproduces rivers/03b.
Taste gate: nothing locked, nothing graduated.
NOT a port. Each fix corrects a faithful reference behaviour that produced a
physically-wrong result, on the developer's explicit call. basinHasLake is KEPT
as the sort. Courses only: no height mutated, no water filled or created —
asserted per seed by a raw-bit digest of both height fields.
- FIX 1 rim cap (ISLA_RIM_CAP_M, default 30 m): a route to the sea that must
climb higher than this above its terminal is refused; the river ends at its
own terminal. Reference routes at any cost (rivers/03 found a 66.7 m one).
- FIX 3 lake targets: a router stops at the nearer of {ocean, significant lake},
so it cannot skirt a lake to reach a distant coast. Reference targets ocean only.
- FIX 2 confluence: courses laid biggest-first join on TRUE cell intersection
(never proximity); the smaller becomes a tributary and adopts the bigger one's
downstream and terminus. Reference lays routes independently — rivers/03 found
two rivers at the identical ocean cell on every seed.
All three are off by default (RiverRouting.Options.Faithful), so rivers/03 still
reproduces bit-for-bit from the same tool.
Taste gate: nothing locked, nothing graduated.
Ports the ROUTING PORTION of the reference's RiverCarvePass (RouteToOcean, the
routed/lake-ender sort, SmoothCourse). NOT CarveRiver (bed stamp) and NOT
AddSteppedWater (water bodies) — those are later tasks.
RED LINE: no height mutated, no water filled, nothing carved. Asserted per seed
by an FNV digest of both height fields before/after routing.
- RiverRouting: deterministic LOWGROUND Dijkstra, uphill penalised so a route may
cross the basin rim, empty-list-on-no-path. Effective == declared constants
(verified: private const, no ConfigManager key, no [Export] in the reference).
- The sort is the REFERENCE's — Kind = basinHasLake ? lake-ender : routed. The
task's stated "a path exists -> routed" cannot discriminate: on an 8-connected
grid a path to the ocean always exists, confirmed empirically (43/43 probes
reached). The ocean route is probed for every giant anyway, so the missing
affordability threshold is reported as a number rather than guessed.
- RegionLabeling.SignificantWaterMask: interim substitute for v2's missing
water-bodies table — 8-connected classify-water components >= 20,000 px.
- RiverCandidates: the candidate enumeration extracted out of RiverPromotionTool
so routing ranks the identical set the count gate was judged on. Behaviour
neutral — rivers/02b's twelve plates are byte-identical across the extraction.
- DrainageRenderer.RoutedMix: three classes, with each routed river's added
lowland reach and the rim it crossed drawn distinctly from its natural stem.
Taste gate: no count, no K, no style, no default set.
