Chapter 3. Sky model families

Table of Contents

3.1. Environment shaders (Sky + analytic shader)
3.2. Discrete light arrays

GroIMP sky models fall into two architecturally distinct families.

3.1. Environment shaders (Sky + analytic shader)

The Sky node wraps a shader implementing computeExitance / computeBSDF. In Twilight (Sunflow raytracer) the sky radiance function is sampled continuously per ray. In GPUFlux it is pre-baked at scene-build time to a 512×512 importance-sampled environment map (FluxSkyLight.discritizeSky()) and serialized to the GPU. Both renderers give physically correct illumination. The background sky colour is visible in rendered images. Sun direction is set as a manual direction vector.

Model Class Parameters
Preetham (1999) Preetham (SunSkyLight) turbidity, sun direction
Hosek-Wilkie (2012) HosekWilkieSkyLight turbidity, ground albedo, sun direction
Prague Sky Model (2021) PragueSkyModelLight dataset file, visibility, observer altitude, ground albedo, sun position