pub fn neptuneshine_irradiance_lux(neptune_phase_fraction: f64) -> f64 {
0.3 + 2.0 * neptune_phase_fraction.clamp(0.0, 1.0)
}
pub fn dark_side_visibility_index(neptune_phase_fraction: f64, terrain_albedo: f64) -> f64 {
neptuneshine_irradiance_lux(neptune_phase_fraction) * terrain_albedo.clamp(0.0, 1.0)
}