3.2. Discrete light arrays

The sky is approximated as a fixed set of directional lights (72–73, Turtle geometry). Works in any renderer. Solar position is computed from geographic coordinates (latitude, day-of-year, hour) via the Goudriaan algorithm. Irradiance is driven by real-world DHI/DNI measurements or CIE sky types. No background image is produced.

Model Class Parameters
Isotropic Overcast SkyDome total power (W/m²)
Perez All-Weather PerezSunSky DHI, DNI, latitude, day-of-year, hour
CIE Standard Sky CIELighting sky type (1–15), cloud cover