2026-08-14

Gap: Riverbank drop depth was a guessed setting

This work closed three gaps: an unmeasured carving setting, a stale-geometry merge bug, and an unwatched terrain defect.

Gap: Riverbank drop depth was a guessed setting

One class of riverbank, where ground drops on a carved channel's low side, used a never-measured cut-depth setting. A read-only pass over every flagged site found a median depth of 0.76 metres, a 90th-percentile depth of 1.63 metres, and confirmed the safety ceiling never applied (9.89 metres of headroom at the closest call). It was replaced with a 2.0-metre ceiling, clamped automatically to the terrain.

The first rebuild showed zero effect: the measurement read depth against smooth ground, not the already-carved ground beneath the water. Correcting it produced 104 corrections at a median depth of 0.79 metres, matching the original diagnosis. A later smoothing pass reintroduced tilt on corrected sites; rerunning the correction after smoothing closed that gap too.

Gap: Stale river geometry could get merged into a fresh build

In-game testing found five visible problems, the most significant a jagged riverbank edge. Rivers excluded from a build for failing validation left old geometry behind, and the merge step combined fresh rivers with geometry up to five days old, producing a visible seam.

Close-up of a freshly rebuilt river course after the stale-geometry bug was fixed — A freshly rebuilt river course, close up, after the fix: current geometry throughout, with no leftover pre-repair edges mixed in.

The fix stamps the build's start time and refuses any river whose saved geometry predates it, rejecting 32 rivers on its first run, mostly leftover tilt corrections. A related timing bug was fixed at the same time: the grass-height texture read pre-carve terrain while the ground rendered the carved version.

Gap: Ground could poke through a flat water surface unnoticed

A screenshot showed ground poking through a flat stretch of river as a visible wedge. A dedicated pass found 2,450 terrain cells with the same problem across the map: ground bulging up between the sample points the existing check tests, not at them.

Histogram of the 2,450 terrain cells where ground pokes through a level water surface, by how far above the water the ground sits — A world-wide count of the wedge defect: 2,450 cells where ground intrudes through a flat water surface between sample points, most by under a metre.

164 rivers are accounted for: 126 freshly rebuilt, 26 kept from a still-valid build, 6 never built, and 6 excluded. The wedge defect carries forward as an open item.