Sky model that implements atmospheric scattering and lighting according to the Sam O’Neil GPU Gems article.
<map> <options> <sky driver = "simple" hours = "0.0" ambient = "0.05" atmospheric_lighting = "true" exposure = "3.0" />
Whether to apply the atmospheric scattering model to the scene under the Sky node. If you set this to false, you will get
basic Phong lighting instead.
Exposure level to apply to the scattering model, which simulates the wash-out effect of viewing terrain through the atmosphere.
hours: Time of day; UTC hours [0..24] ambient: Minimum ambient lighting level [0..1] to apply to dark areas of the terrain