Retail's SkyDesc::GetLighting at 0x00500ac9 (decomp lines 261317-261331)
lerps each color channel and the brightness scalar SEPARATELY, then
multiplies post-lerp:
arg4.r = lerp(k1.amb_color.r, k2.amb_color.r, u)
arg4.g = lerp(k1.amb_color.g, k2.amb_color.g, u)
arg4.b = lerp(k1.amb_color.b, k2.amb_color.b, u)
arg3 = lerp(k1.amb_bright, k2.amb_bright, u)
final = (arg4.rgb * arg3, ...)
acdream pre-multiplied (color × bright) at LOAD time
(`SkyDescLoader.cs:558-559`) and then lerped the product. For any
keyframe pair where both color and brightness change, the two are
mathematically distinct. Example, k1=(white, b=0.5) k2=(black, b=1.0)
at u=0.5:
- retail: color=gray(0.5), bright=0.75 → final = (0.375, 0.375, 0.375)
- acdream: lerp((0.5,0.5,0.5), (0,0,0), 0.5) = (0.25, 0.25, 0.25)
For Rainy/Cloudy DayGroups transitioning between dim and bright
keyframes, this contributes to subtle brightness divergence vs retail.
Refactor:
SkyKeyframe stores DirColor / DirBright / AmbColor / AmbBright
SEPARATELY (raw, not pre-multiplied).
Computed properties SunColor and AmbientColor return the
post-multiplied product, keeping the shader uniform interface
(uSunColor / uAmbientColor) unchanged.
SkyStateProvider.Interpolate lerps each raw channel, then constructs
a new SkyKeyframe whose computed properties yield the correct
post-lerp multiply.
SkyDescLoader now stores raw values without pre-multiplying.
GameWindow comment updated; no functional change there.
Default factory + tests updated to use the new constructor parameters
with DirBright=AmbBright=1.0 (preserving exact existing behavior).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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>
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>
Client-side deterministic sky + weather + day/night system per R12.
Retail's model is 95% client-side: the server just delivers its
current PortalYearTicks (double, seconds since boot-seed) at login and
in TimeSync packets; the client computes everything else locally from
the constants in r12 §1.2 + ACE DerethDateTime.cs.
Core layer (AcDream.Core/World):
- DerethDateTime: retail-exact calendar (16 hours/day, 30 days/month,
12 months/year, 7620 ticks/day, 2,743,200 ticks/year). HourName enum
covers all 16 named half-hour slots (Darktide → GloamingAndHalf);
MonthName covers the 12 Derethian months (Snowreap → Frostfell).
DayFraction, CurrentHour, IsDaytime, ToCalendar.
- SkyKeyframe + SkyStateProvider: 4-keyframe default day/dawn/noon/dusk
with linear color + angular-wrap heading interpolation + slerp-like
shortest-arc lerp so heading wraps 350° → 10° don't tween backwards
through 180°. Default keyframe colors tuned to retail screenshots
(sunrise warm, noon white, sunset red, midnight deep blue).
- WorldTimeService: owns the live clock. SyncFromServer(ticks) sets
baseline; NowTicks advances by real-time elapsed. Exposes DayFraction,
CurrentSky, CurrentSunDirection, IsDaytime for the render thread.
This is the foundation Phase G.2 (dynamic lighting) consumes: lighting
uniforms are fed from CurrentSky's SunColor / AmbientColor / sun
direction, varying smoothly across the day.
Tests (16 new):
- DerethDateTime: midnight, half-day, wrap, Dawnsong, Midsong,
day/night flag at dawn vs Darktide-Half, year rollover, month
advance.
- SkyState: 4-default keyframes, noon-exact matches frame data,
midpoint lerps between neighbours, wrap across midnight doesn't
produce NaN, sun direction returns unit vector, WorldTimeService
sync + DayFraction at noon.
Build green, 587 tests pass (up from 570).
Ref: r12 §1 (Portal Year math), §2 (sky objects), §4 (color lerp).
Ref: ACE DerethDateTime.cs + NetworkSession TimeSync handler.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
