question was “how is it lit?” and obviously, if you have a whole world inside a sphere, what would be in the middle of that sphere? the sun! or whatever the light source of this world is.
art of the title: it’s interesting that you were trying to answer these practical problems even though it would eventually be created all in the computer. you're still asking questions like, "well what's beyond the horizon, is it a room? oh, so let's make it a sphere" or "how do you light it?" as opposed to just saying "well it's lit."
angus wall: one thing that was really important was to make it feel like 