World and levels › Large worlds
Air and distance: fog, sky and time of day
Know first: Direct and indirect light, Fog and post-processing
Air gives the sky its color, turns sunsets red, makes haze white and the distance blue. Without it, a huge world looks like a model on a table. This lesson explains how light scatters off molecules and haze, and covers aerial perspective, time of day and weather. It ends with how the sky, sun, fog and clouds in Unreal work as one system.
Why this matters
Imagine a world without air, like the Moon. The sky is black even by day, the shadows are black, and a mountain thirty kilometers away is as sharp and dark as the rock under your feet. The eye has nothing to judge distance by, so a huge world reads as a model on a table.
Air does three things at once. It colors the sky and the light of the sun. It pushes the distance back, turning it pale and blue. And together with the sun it paints the time of day and the weather.
The lesson on post-processing explains how fog dims light along its path. This page is about where air gets its color and how an artist can control it.