Ran a live memory probe against retail acclient.exe (new tool:
tools/RetailTimeProbe/) to read the TimeOfDay struct at
DAT_008ee9c8 and compare against our computed values. The decompile
agent's identification of TimeOfDay+0x10 as "SecondsPerDay (int
copy)" turned out to be WRONG — the live value is **360**, which is
GameTime.DaysPerYear.
The retail FUN_00501990 LCG seed is:
seed = Year × (*+0x10) + DayOfYear
= Year × DaysPerYear + DayOfYear
= flat "total days since epoch" day-index
Our previous Phase 3c port passed 7620 (DayLength in ticks) as the
multiplier, producing seed=883,967 against retail's seed=41,807 —
completely different LCG outputs, completely different DayGroup
picks. That's why the user's retail kept showing stormy/rainy while
acdream showed sunny/clear (or vice versa) even after Phases 3c.1
and 3f aligned Year and DayOfYear.
Also confirmed by the probe:
- EpochBase / ZeroTimeOfYear = 3600 ✓ Phase 3f already correct
- BaseYear / ZeroYear = 10 ✓ DerethDateTime.ZeroYear
- Year=116, DayOfYear=47 ✓ our AbsoluteYear / DayOfYear
- SecondsPerDay float (+0x0C) = 7620 ✓ DayTicks
- SecondsPerYear = 2,743,200 ✓ YearTicks
One "finding that's not a fix": retail's +0x48 DayFraction is a
sub-period fraction (fraction through current day/night window)
NOT a full-day fraction. CurDayEnd - CurDayStart = 2857.5 = 0.375
of a day = 6 Dereth hours = night duration. Not relevant for our
keyframe bracket interpolation, which correctly uses a full-day
0..1 scale matching the SkyTime.Begin values. Documented in the
probe research doc so future work doesn't trip on it.
Changes:
- tools/RetailTimeProbe/ — new P/Invoke tool. Forced x86 target to
match retail's bitness so hardcoded DAT_xxxxxxxx addresses are
pointer-width-correct. Handles ASLR relocation via
Process.MainModule.BaseAddress.
- src/AcDream.App/Rendering/GameWindow.cs: RefreshSkyForCurrentDay
passes 360 (DaysInAMonth × MonthsInAYear) not 7620.
- src/AcDream.Core/World/SkyDescLoader.cs: ActiveDayGroup(ticks)
and DefaultDayGroup same.
- docs/research/2026-04-23-retail-memory-probe.md — full probe
results + decompile-agent correction.
- AcDream.slnx — add tools/ folder.
Build + 733 tests green.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
1e1d3875f7