C asked in THREADS whether to land a one-liner making gardenHailExposure read
sail.porosity. Answer: it is already wired, in merged main — I did it in SPRINT9
(e576f5c): skyfx.step refreshes sailPorosity from world.sail.porosity, and
gardenHailExposure folds hailBlockFor(size, sailPorosity) into what it returns.
No one-liner needed.
But "already wired" was untested end-to-end. The only test of the hail leak,
weather.selftest's 'fabric choice is real', REIMPLEMENTS the formula inline with
hailBlockFor + hailAt — it proves the primitive and the arithmetic, not the
plumbing. A regression in the plumbing (the :738 refresh dropped, the
wind.def.hail.size lookup resolving wrong, hailBlockFor no longer folded in)
would leave that test green while the game quietly stopped leaking hail. That is
the measure-a-copy pattern this whole browser suite exists to avoid.
New assert 'porous cloth leaks pea hail into the garden, membrane blocks it'
drives the real sky.gardenHailExposure. The isolation is exact: ONE settled,
intact rig, sampled at ONE hail instant, porosity flipped 0.30<->0 between reads.
sky.step(0, t, {sail}) refreshes sailPorosity and rebuilds the shadow grid at the
same instant without advancing physics, so shadow geometry is identical across
the two reads and `block` is the only thing that moved. Measured:
pea (size 0.7): cloth 0.346 vs membrane 0.292 -> porous leaks +18%
ice (size 1.4): cloth 0.458 vs membrane 0.458 -> identical, the no-op
No storm flight, no second rig — deliberately. Two rigs whose corners diverge
share no shadow, and that difference is a cascade not a fabric: membrane cascades
on the ice night, so a naive two-flight version reads a FALSE ice-night
difference. The same-rig swap removes it.
And it can fail: if porosity stops reaching the exposure, both reads collapse to
the membrane value (measured: 0.2917 == 0.2917), cloth > membrane*1.05 is false,
red. The ice check is exact equality — if porous ever starts leaking big ice,
that goes red too.
Selftest 288 passed, 0 failed, 0 skipped.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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