Multi-layered Skyboxes

Multi-layered skyboxes are no different from regular skybox work but like you said depending on the needs they might have to be animated in different ways. For example, on Halo 5, I had to work on a space elevator sequence where the player has to go from space all the way to the surface of a planet. Now that was not an easy problem to solve because no one really knew how exactly to solve this issue because it had pretty much never been done before in a game. It was a great problem solving exercise for me! What we ended up doing was, I made 3 skyboxes (one for the planetary view from space, one for the stratospheric level and one for the terrain level) one below the other and the animation team animated them upward, which made it look like the elevator moved downwards. The parts where there was a hard transition from one skybox to another, we made the elevator go into a covered section so that the transition will be appear to be seamless to the player.