Two independent investigations (in-house decomp re-check + two
external agent reports) converged on the same root cause for the
"too blue-white sky" symptom:
acdream computed SunColor = DirColor × DirBright and AmbientColor =
AmbColor × AmbBright. Retail computes them from the magnitude of a
specially-shaped sun vector instead. Per the named retail decomp:
SkyDesc::GetLighting at 0x00500ac9 (decomp 261343-261353):
sunVec.x = sin(H_rad) × DirBright × cos(P_rad)
sunVec.y = cos(P_rad) ← NOT scaled by DirBright
sunVec.z = DirBright × sin(P_rad)
PrimD3DRender::UpdateLightsInternal at 0x0059b57c (decomp 424118):
D3DLIGHT9.Diffuse.r = sunlight_color.r × sqrt(x²+y²+z²)
SmartBox::SetWorldAmbientLight callsite at 0x0050560b (decomp 267117):
SetWorldAmbientLight(sqrt(|sunVec|²) × 0.2 + ambient_level, ...)
Y stays unscaled by DirBright on purpose, so |sunVec| ≠ DirBright in
general — the magnitude varies with sun pitch/heading. That's what
gives retail's "sun feels stronger when it's overhead, ambient warms
up at midday" behavior we were missing.
Added SkyStateProvider.RetailSunVector(kf) that builds the vector
verbatim. SkyKeyframe.SunColor / AmbientColor now compose via |sunVec|.
SunDirectionFromKeyframe normalizes the same vector (replaces our
geometrically-clean spherical convention which didn't match retail's
deliberate Y-decoupled-from-heading shape).
Tests:
- Replaced the linear-interp assumption in
Interpolate_BetweenKeyframes_LerpsColors with a test on the RAW
inputs (DirColor, AmbBright, etc.) — those still lerp linearly;
the composite SunColor doesn't, intentionally.
- Added 4 golden-value tests for the new formulas
(RetailSunVector_AtZenith, _AtHorizonNorth,
SunColor_UsesRetailMagnitudeNotDirBrightDirectly,
AmbientColor_BoostsByTwentyPercentOfSunVectorLength).
- Updated stale LoadFromRegion_SunColor_IsPrepreMultipliedByBrightness
test to LoadFromRegion_SunColor_UsesRetailSunVectorMagnitude
with the new expected magnitude.
User visually verified — acdream's sky shifted from blue-white toward
the warm tint retail shows at the same keyframe.
1227 tests pass.
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>
