User-observed regression 2026-04-23: acdream spawned rain particles
when retail showed no rain at the same server tick. Root cause: my
Phase 3e shortcut mapped DayGroup.Name = "Rainy" → WeatherKind.Rain →
rain particle emitter. That's not what retail does.
Parallel decompile research confirms:
- Agent A (2026-04-23-physicsscript.md): PhysicsScript runtime lives
at FUN_0051bed0 → FUN_0051bfb0, runs per PhysicsObj; sky calls it
from NOWHERE.
- Agent B (2026-04-23-sky-pes-wiring.md): FUN_00508010 (sky render
loop) never reads SkyObject.DefaultPesObjectId — the field is dead
at render time. Rain/snow particles in retail come from a separate
camera-attached weather subsystem that has NOT yet been located.
So the correct behavior is: DayGroup name should only drive
fog/ambient tone (via keyframes, already in the Snapshot path),
never spawn particle emitters. Any retail-faithful particle rain
belongs to a future phase once we find the camera-attached weather
subsystem driver.
Change: MapDayGroupNameToKind now maps all weathery substrings
(storm/snow/rain/cloud/overcast/dark/fog) → Overcast — fog-only
visuals, no particle spawn. Clear names stay Clear. The Rain, Snow,
Storm enum values remain and are still accessible via ForceWeather()
for debug overrides.
Tests updated (WeatherSystemTests): the name→kind theory now expects
Overcast for Rainy/Snowy/Stormy variants.
Also commits the four research docs from this session's parallel
hunt: PhysicsScript dat+runtime, sky↔PES wiring (negative finding),
lightning timer (negative finding — agent #3), fog on sky
(positive: retail applies fog to sky geometry).
NOTE on lightning: agent #3's research only ruled out the CLIENT-SIDE
RANDOM TIMER hypothesis for lightning. User confirms retail does have
visible lightning + thunder. A follow-up agent (#5, in flight as of
this commit) is hunting the real mechanism — PlayScript opcode,
SetLight PhysicsScript hooks, AdminEnvirons side effects, or the
weather-volume draw. This commit does NOT attempt to port lightning.
Build + 733 tests green.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
User reported rain in acdream while retail showed a clear sunny sky
after Phase 3d landed. Root cause: two independent weather systems
running in parallel.
1. Retail DayGroup picker (FUN_00501990 port, Phase 3c/3c.1) —
selected DayGroup[6] "Sunny" correctly.
2. WeatherSystem.Tick (legacy stub from pre-decompile era) —
kept rolling its own hardcoded PDF every day (60% Clear, 20%
Overcast, 12% Rain, 5% Snow, 3% Storm), independent of the
DayGroup picker. Its output drove the rain/snow particle
emitters via UpdateWeatherParticles. If its hash happened to
land on Rain for today's dayIndex, rain rendered even on a
Sunny DayGroup day.
Retail has ONE source of truth for weather: the DayGroup roll. There
is no separate weather state machine — rain/snow/storm are implied by
the DayGroup name and its per-keyframe SkyObjectReplace settings.
Fix (Phase 3e):
- WeatherSystem.SetKindFromDayGroupName(string?) — loose substring
match on the retail DayGroup name: "storm" → Storm, "snow" → Snow,
"rain" → Rain, "cloud"/"overcast"/"dark"/"fog" → Overcast, else
Clear. Case-insensitive. Covers the names observed in the live
Dereth dat dump (Sunny, Clear, Cloudy, Rainy + inferred variants).
- WeatherSystem._externallyDriven flag disables the internal
RollKind auto-roll once SetKindFromDayGroupName has been called at
least once. Tests that drive Tick() directly keep the legacy
hash-roll behavior (offline fallback). ForceWeather still works
for debug overrides.
- GameWindow.RefreshSkyForCurrentDay calls
Weather.SetKindFromDayGroupName(grp.Name) right after it installs
the new SkyStateProvider. Logs the resulting WeatherKind on the
same line as the DayGroup pick for correlation.
- New WeatherSystemTests.SetKindFromDayGroupName_MapsRetailNames
(theory, 14 cases) + SetKindFromDayGroupName_DisablesInternalRoll.
Expected effect: Sunny/Clear DayGroups → no rain emitter. Rainy/Stormy
DayGroups → rain emitter active. The user's specific scenario
(DayGroup[6] "Sunny") now correctly maps to WeatherKind.Clear and no
particles spawn.
Build + 733 tests green (+16 new).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Expand the SkyKeyframe record with retail-exact fog fields (FogStart,
FogEnd, FogMode) per r12 §5. The existing FogDensity field is retained
for backwards compat with tests that pin it; new shipping code reads
FogStart / FogEnd / FogMode directly.
Add WeatherSystem (WeatherKind + EnvironOverride enum + 10s transition
ease + deterministic per-day-index roll) matching r12 §6.1. Roll weights
are ~60% Clear / 20% Overcast / 12% Rain / 5% Snow / 3% Storm — tuned
against retail observations. Storm mode triggers lightning flashes
every 8–30 s via an exponential-decay (200ms τ) flash level that the
shader consumes as an additive scene bump.
Add SkyDescLoader that parses the Region dat (0x13000000) into
LoadedSkyDesc — DayGroupData with SkyObjectData (visibility window +
arc sweep), per-keyframe SkyObjectReplaceData, and a shader-ready
SkyStateProvider builder. Sun/ambient colors are pre-multiplied by
DirBright/AmbBright so the shader never needs to know about retail's
scalar brightness field.
19 new tests (weather determinism, transition ease, environ override
tint, flash decay, dat-load conversion with fog + pre-mult colors).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
