VerticalShaftEquivalence is bit-identical (966 samples inside a shaft), so operator
reuse across archetypes is measured now, not intended.
But SurfaceHeightEquivalence failed: 69/20000 overhang samples differ, 1 crossing the
isosurface. Cause is the ColumnKey from f3faa3b, which was
hash(StrateBottomWorldZ, LayoutVersion, Seed) and omitted the params. Two stacks of
the same strate with different overhang settings therefore shared a key, and the
second read the first's columns, computed with OverhangAmp = 0. The overhang silently
vanished wherever a column was already cached.
Not a test artifact: this is the weakness the codebase already documents for
GSurfColCache (extended AUDIT C2 note) — a live edit that changes params without
moving the strate leaves the key unchanged and serves stale columns. Production masks
it because RebuildStrates bumps LayoutVersion; my key inherited the hole.
Fixed by folding an FCrc::MemCrc32 fingerprint of the params, and of every per-biome
param set, into the key. FSurfaceGenerationParams is verified pure POD, so a memory
CRC cannot produce a false hit; padding can only cause a false miss, i.e. a recompute.
A perf optimisation introduced a correctness bug and the tests caught it the same
day. The failure was invisible to inspection and produced plausible terrain.
Known and not fixed: VerticalShafts proves 0 of 60 tiles because EffectOverBox
returns CarveOnly whenever any shaft sits within a Spacing*1.6 halo rather than
testing real connector capsules. Pessimistic, not wrong — lost CPU, never a hole.
UNVERIFIED: not compiled.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Fr0zka
d0a9ce3018