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fix(simulation): PR #197 review round — real seaward chord for Mouth edges (Hoshe #1/#2, Tyre 1/2)

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The batch's real bug: extract_river_network computed the seaward
neighbor (nr,nc) to decide the MOUTH sentinel then discarded it, and
build_edges placeholder-pointed mouth edges at themselves — zero
chord, invent_course's degenerate 1-point return, resolve_mouth_
terminus dead code on real data, ALL real mouths resolving None, and
(because Ruling 3g retired the D/Q clip on the promise of real
termini) mouths vanishing at District/Quarter. The second instance of
the threw-away-the-answer anti-pattern Ruling 2b fixed for interior
pointers. Fix: river_seaward: Vec<(u16,u16)> on RiverNetwork
(additive, serde-default, parallel array; meaningful only at MOUTH
entries), captured in the same extraction pass; build_edges gives
Mouth edges the real one-D8-step chord. Permanent acceptance:
all_real_gj1c_mouths_resolve_to_mouth_terminus_not_none — 3/3, revert-
verified failing at the golden's first mouth (38,47). Mouth golden
coverage added (river_course_golden gains district_mouth/quarter_mouth
samples + non-degeneracy test; the previously Interior-only filter
gap closed). Tyre 1: the land-probe's dead dx/len*len arithmetic
replaced — station_spacing_m threaded through the crop path, probe
steps one real cell spacing, comment reconciled. Tyre 2: boxing
comment reattributed to variant-size balancing (Layer1Output retention
lives on TerrainAnalysisCache, not BodyWorldState). Hoshe #4:
cascade_golden's doc now states the attractor cascade accurately
(count-parity, not byte-identity — water_dist seeds from mouths).
Full cargo test green; goldens re-pinned deliberately; bench +3.0%.

Tickets: T-1170

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
This commit is contained in:
jpmschweitzer
2026-07-23 15:02:16 +02:00
co-authored by Claude Fable 5
parent 581be31549
commit d256233faf
10 changed files with 2325 additions and 53 deletions
Download Patch File Download Diff File Expand all files Collapse all files
server/src/atlas/layer_proxy.rs
+163 -4
View File
@@ -1237,6 +1237,11 @@ fn invent_courses_near_window(
/// Crop the window's already-invented courses ([`invent_courses_near_window`])
/// to the wire [`RiverCourse`] shape (Ruling 3h) — window rect + one station
/// beyond each edge, terminus resolution (A3, Ruling 3e/3f).
///
/// `station_spacing_m` is the rung's own cell spacing (`granularity.spacing_m()`
/// — District 2,048 m / Quarter 512 m) — threaded to [`resolve_mouth_terminus`]'s
/// land-at-final-anchor probe, which extends "one cell length" (Ruling 3e's own
/// words), not one Stage-B segment length (Tyre, PR #197 review issue 1).
#[allow(clippy::too_many_arguments)]
fn crop_courses_for_wire(
invented: &[InventedCourse],
@@ -1247,6 +1252,7 @@ fn crop_courses_for_wire(
ta: &crate::atlas::features::TerrainAnalysis,
climate: &crate::atlas::district_profile::ClimateConstants,
min_wavelength_m: f64,
station_spacing_m: f64,
) -> Vec<RiverCourse> {
invented
.iter()
@@ -1260,6 +1266,7 @@ fn crop_courses_for_wire(
ta,
climate,
min_wavelength_m,
station_spacing_m,
)
})
.collect()
@@ -1280,6 +1287,7 @@ fn crop_course_to_window(
ta: &crate::atlas::features::TerrainAnalysis,
climate: &crate::atlas::district_profile::ClimateConstants,
min_wavelength_m: f64,
station_spacing_m: f64,
) -> Option<RiverCourse> {
let (x0, y0, x1, y1) = window_rect;
let inside = |p: &(f64, f64)| p.0 >= x0 && p.0 <= x1 && p.1 >= y0 && p.1 <= y1;
@@ -1328,6 +1336,7 @@ fn crop_course_to_window(
ta,
climate,
min_wavelength_m,
station_spacing_m,
) {
Some(mouth_point) => {
// Replace the cropped course's tail with the resolved
@@ -1373,6 +1382,12 @@ const MOUTH_BISECT_ITERATIONS: u32 = 6;
/// probe past the final anchor) samples water, returns `None` — the
/// degenerate "drawn coast receded past this edge" case (Ruling 3e), which
/// the caller renders with no mouth flag.
///
/// `station_spacing_m` is the rung's own cell spacing — the probe extends
/// exactly "one cell length" past the final anchor (Ruling 3e's own words),
/// in the direction of the final Stage-B segment, but scaled to
/// `station_spacing_m` rather than that segment's own (possibly much
/// shorter, near-zero at a taper-to-zero anchor) length.
fn resolve_mouth_terminus(
course: &InventedCourse,
seed: SeedChain,
@@ -1381,6 +1396,7 @@ fn resolve_mouth_terminus(
ta: &crate::atlas::features::TerrainAnalysis,
climate: &crate::atlas::district_profile::ClimateConstants,
min_wavelength_m: f64,
station_spacing_m: f64,
) -> Option<(f64, f64)> {
let is_water = |p: (f64, f64)| -> bool {
// `&[]`: the mouth-termination water-verdict probe has no use for
@@ -1418,16 +1434,19 @@ fn resolve_mouth_terminus(
}
prev_land = p;
}
// Final anchor still land: extend one cell length along the segment's
// own direction as a single probe (Ruling 3e: "extend along the D8
// direction up to one cell length probing").
// Final anchor still land: extend ONE CELL LENGTH (`station_spacing_m` —
// Ruling 3e's own words, "up to one cell length probing", not one
// Stage-B segment length, which can be much shorter near a
// taper-to-zero anchor — Tyre, PR #197 review issue 1) along the final
// segment's own direction, as a single probe.
if pts.len() >= 2 {
let a = pts[pts.len() - 2];
let b = pts[pts.len() - 1];
let (dx, dy) = (b.0 - a.0, b.1 - a.1);
let len = (dx * dx + dy * dy).sqrt();
if len > 1e-6 {
let probe = (b.0 + dx / len * len, b.1 + dy / len * len); // one more segment-length step
let (ux, uy) = (dx / len, dy / len); // unit direction of the final segment
let probe = (b.0 + ux * station_spacing_m, b.1 + uy * station_spacing_m);
if is_water(probe) {
return Some(bisect_to_waterline(b, probe, is_water));
}
@@ -1589,6 +1608,7 @@ pub fn build_district_window_layer(
ta,
climate,
min_wavelength_m,
step_m,
);
DistrictWindowLayer {
@@ -1686,6 +1706,7 @@ fn build_district_window_layer_serial(
ta,
climate,
min_wavelength_m,
step_m,
);
DistrictWindowLayer {
center,
@@ -2946,6 +2967,144 @@ mod tests {
}
}
/// **T-1170 PR #197 review, Hoshe #1 acceptance test (blocking, permanent
/// — not a throwaway probe).** Every real Mouth edge on the GJ1c golden
/// fixture (256×128 downsample, the SAME fixture `cascade_golden.rs`
/// pins — 3 mouths: `[(38,47), (38,98), (124,239)]`) must resolve
/// `CourseTerminus::Mouth`, not `CourseTerminus::None`.
///
/// **What this guards:** before the fix, `build_edges` set
/// `downstream = upstream` for every Mouth edge (a same-cell
/// placeholder — the SAME discard-then-need-it-later anti-pattern
/// Ruling 2b's `river_downstream` field fixed for interior pointers,
/// applied a second time to the seaward neighbor `extract_river_network`
/// already computes and then threw away). That zeroed the chord
/// (`chord_m < 1.0`), which tripped `invent_course`'s degenerate
/// single-point return, which made `resolve_mouth_terminus`'s station
/// walk a no-op (a 1-point course can't reach the `pts.len() >= 2`
/// fallback probe either) — all 3 real GJ1c mouths silently resolved
/// `CourseTerminus::None` instead of `Mouth`, and since Ruling 3g retired
/// the District/Quarter draw-time clip on the promise of real termini,
/// mouths would have disappeared entirely at those rungs. The fix:
/// `RiverNetwork::river_seaward` (additive, captured in the same
/// `extract_river_network` pass) carries the real seaward neighbor
/// through to `build_edges`, giving Mouth edges a genuine ~one-cell
/// chord to invent a course along.
#[test]
fn all_real_gj1c_mouths_resolve_to_mouth_terminus_not_none() {
use crate::atlas::drainage;
use crate::atlas::heightmap::load_heightmap_png;
use crate::atlas::river_course;
let src = std::path::PathBuf::from(env!("CARGO_MANIFEST_DIR"))
.join("../wiki/star-systems/GJ-1/bodies/GJ1c/heightmap.png");
let heightmap =
load_heightmap_png(&src, "GJ1c", 0.3).expect("decode committed GJ1c heightmap");
let small = heightmap.downsample(256, 128);
let dr = drainage::analyze(&small.data, small.width, small.height, small.sea_level);
let ta = crate::atlas::features::TerrainAnalysis::analyze(&small, &dr);
let rn = &dr.river_network;
let params = crate::atlas::district_profile::BodyParams {
hydrosphere: Some("ocean".into()),
atmosphere: Some("breathable".into()),
planet_class: Some("temperate".into()),
body_radius_km: Some(6371.0),
..Default::default()
};
let climate = crate::atlas::district_profile::ClimateConstants::default();
let seed = SeedChain::root(0xC0FFEE_u64).derive(SeedDomain::Body, 1);
let station_spacing_m = DISTRICT_M as f64;
let edges = river_course::build_edges(rn);
let mouth_edges: Vec<_> = edges
.iter()
.filter(|e| e.terminus == river_course::EdgeTerminusKind::Mouth)
.collect();
assert_eq!(
mouth_edges.len(),
rn.mouths.len(),
"build_edges must produce exactly one Mouth edge per RiverNetwork.mouths entry"
);
assert_eq!(
mouth_edges.len(),
3,
"GJ1c at this downsample is expected to have 3 real mouths (matches the \
committed cascade_golden fixture) — if this count changes, re-verify against \
tests/golden/cascade_layer1.json before updating this assertion"
);
let mut resolved_mouth_count = 0;
for edge in &mouth_edges {
// Sanity: the fix means Mouth edges get a real, non-degenerate
// chord toward the seaward neighbor — never upstream==downstream.
assert_ne!(
edge.upstream, edge.downstream,
"Mouth edge {:?} still has a same-cell placeholder downstream — \
river_seaward threading regressed",
edge.edge_id
);
let course =
river_course::invent_course(seed, edge, &ta, &params, station_spacing_m, 0.0);
assert!(
course.points.len() >= 2,
"Mouth edge {:?} invented a degenerate {}-point course — the chord-length \
fix regressed",
edge.edge_id,
course.points.len()
);
// Window rect generous enough to contain the whole short mouth
// course (mouths are ~one cell chord, so a wide margin is cheap).
let (min_x, max_x) = course
.points
.iter()
.fold((f64::INFINITY, f64::NEG_INFINITY), |(lo, hi), p| {
(lo.min(p.0), hi.max(p.0))
});
let (min_y, max_y) = course
.points
.iter()
.fold((f64::INFINITY, f64::NEG_INFINITY), |(lo, hi), p| {
(lo.min(p.1), hi.max(p.1))
});
let margin = 50_000.0;
let window_rect = (min_x - margin, min_y - margin, max_x + margin, max_y + margin);
let wire = crop_course_to_window(
&course,
window_rect,
seed,
"GJ1c",
&params,
&ta,
&climate,
0.0,
station_spacing_m,
)
.unwrap_or_else(|| panic!("Mouth edge {:?} cropped to nothing in its own window", edge.edge_id));
assert_eq!(
wire.terminus,
CourseTerminus::Mouth,
"Mouth edge {:?} (upstream {:?}, downstream {:?}) resolved {:?} instead of \
CourseTerminus::Mouth",
edge.edge_id,
edge.upstream,
edge.downstream,
wire.terminus
);
resolved_mouth_count += 1;
}
assert_eq!(
resolved_mouth_count, 3,
"acceptance criterion (Hoshe #1): all 3 real GJ1c mouths must resolve \
CourseTerminus::Mouth"
);
}
/// Clamped-window edge: `n = 1` is the minimum valid window (a single
/// district) — no panic, no empty output, exactly one cell per array.
#[test]