2026-08-28

Gap: Waterfall body was a flat ribbon

The water renderer used a flat, ribbon-shaped mesh for falling water, and an arbitrary brightness clamp to decide where whitewater should appear. Both were replaced.

Gap: Whitewater intensity had no physical basis

A 2018 hydropower turbine-efficiency paper expresses specific energy as a height drop plus a velocity term, mapping onto channel data the terrain pipeline already tracks. A baked specific-energy value at every river point now drives whitewater intensity, fading downstream of a drop instead of switching off abruptly.

Gap: Waterfall body was a flat ribbon

Reviewing the new rule surfaced a separate problem: the waterfall body was a flat ribbon mesh, a placeholder that read wrong next to the tuned whitewater. It was replaced on every waterfall with a three-stage body: a tight curtain at the lip, a fan widening partway down, and a flat splash apron at the base, checked against reference photographs, judged correct at medium distance.

A finer step size for quantizing whitewater intensity was chosen over a coarser option after scanning 25,039 points: the two agreed at 93.4 percent of sites, and the roughly 1,600 where they differed were low-gradient channels, where the coarser setting merged small falls the finer kept distinct.

A full rebuild ran both rules together: 164 courses rebuilt with matching waterfall-body geometry, zero seam defects across 70 checks, zero mesh cracks across 448,558 vertices, and 26 of 26 known defects caught under mutation testing. One signal, falls near a river junction, rose from 22 to 32, unexplained; a dedicated exception is open.

Gap: Small waterfalls rendered wrong under the new body

The three-stage body, scaled to a two-meter drop, produced a glassy transparent curtain under a full-size mist cloud, where a small real fall instead runs white with foam and lands in a wide, low band. The fix added one dial and a blend: below a six-meter drop the glassy portion shrinks, a foam texture whitens the water from the lip down, and mist shrinks with drop height while the foam band keeps width; above six meters the body applies unchanged. Sixteen of the 164 water courses fall under that threshold. The map was rebuilt the same day.