We had made some ZDoom levels with sun angle simulation, which was a built-in feature now (as opposed to having to make tons of fake sectors all over). But actually the angle was static for each level. The direct sunlight looked nice on the walls, and the opposite walls were dark, as they should be. (Usually north-south walls are shaded one way, east-west ones a different shade, and diagonal ones in-between, but apparently having a sun angle set for the level put it into a different wall-shading mode).