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>
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