Diagnosed the "retail shows early night, acdream shows early day" time
mismatch: server time sync was working correctly (ticks=291079558 →
dayFraction=0.8546 → EvensongAndHalf, hour 14 of 16). The mismatch was
the hardcoded DayGroup index.
Dereth's SkyDesc carries 20 DayGroups (Sunny / Clear / Cloudy / Storm /
etc), each weighted at ChanceOfOccur=5.0. Retail rolls one per server
day by `ChanceOfOccur` as a PDF (r12 §11). We were always rendering
DayGroup 0 = "Sunny" regardless of day, so at EvensongAndHalf we showed
SkyTime[7]@0.84 — sun still 20° above the western horizon, warm golden
— i.e. pre-sunset rather than the dimmer pre-night appearance retail
shows after rolling a cloudier group.
Fix (Phase 3a):
- LoadedSkyDesc.SelectDayGroupIndex(dayIndex) — deterministic roller:
SplitMix64 hash of dayIndex → normalize to [0, sumChances) → walk the
cumulative distribution. Same dayIndex on every client = same weather
on every client, zero network sync needed.
- LoadedSkyDesc.ActiveDayGroup(ticks) / BuildProviderForDay(ticks) —
convenience wrappers that compute dayIndex from raw server ticks.
- ACDREAM_DAY_GROUP=<N> env var override. Set to 10 "Clear", 12 "Cloudy",
etc. for A/B visual verification against retail.
- SyncFromServer gains a [sky-dump] log: `ticks=X dayFraction=Y
calendar=PY{year} {month} {day} {hour}` so the time-sync state is
auditable from a single grep.
- GameWindow: tracks _loadedSkyDayIndex + _activeDayGroup. Calls
RefreshSkyForCurrentDay on every server sync — swaps WorldTime's
provider + caches the group only when the day index crosses a
boundary (idempotent within a single day). SkyRenderer.Render now
consumes _activeDayGroup instead of the legacy DefaultDayGroup.
Observed (this session, local ACE):
server sent ticks=291079558 → PY106 ColdMeet 10 EvensongAndHalf
SplitMix64(day 38197) will deterministically pick one of 20 groups.
Build + 717 tests green. Ready for user visual verification with
retail side-by-side.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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