Technical director Alan Roberts breezes through the ins-and-outs of a real-life optical phenomenon known as Rayleigh scattering, which is what causes both the vivid blue hue of the midday sky and the red and yellow tones of the sky at sunset. In a nutshell, the sky in Horizon 2 is blue because science dictates it, not because an artist glanced out a window and settled on the closest shade he or she could find.
This now means that we can simulate the way that light interacts with particles in the atmosphere, says Roberts. We no longer have to have artists picking the colour of the sky from a colour picker; we can model the amount of particles in the atmosphere and the sky and the lighting reacts accordingly.
Thats how it works in real-life, and thats exactly how its working here, adds Penrose.
The pair go one step further, stripping away the particles from Horizon 2s atmosphere. We can now see the stars (which Penrose assures us are also accurately modelled) because, as Taylor explains, ts like being on the moon or a planet without an atmosphere.