Time of day 0–1 (0 = midnight, 0.5 = noon).
Unit vector toward the sun — below the horizon at night (y < 0).
Unit vector toward the moon (always opposite the sun).
Direction of the active luminary: the sun by day, the moon by night.
Color of the active luminary (warm-shifted near the horizon).
DirectionalLight-scale intensity of the active luminary.
Sky/background color for this moment — the same value as skyHorizon.
Sky color at the horizon. A SkyDome hazes the world into this, so the map edge and the sky meet in one value.
Sky color straight overhead — the top of the dome's gradient.
uLightColor value for the terrain shader (lightColor pre-scaled by intensity, matching the material's static defaults at noon).
uAmbient value for the terrain shader.
Multiplier for unlit liquid surfaces (see setLiquidLightTint) — white at noon, dark blue at night, so lava's emissive glow carries the scene.
0 at night → 1 in full day (twilight ramps between).
True while the sun is below the horizon (the moon is the active light).
Everything a renderer needs to light one moment of the cycle. All objects are reused between evaluate() calls — copy, don't keep.