Concerning night sceneries as seen from high altitudes, especially for big cities, I made some tests over Paris using approximatly 40x40km of baked night textures generated by an algorithm I developed (that uses OSM data).
Not a big impact on performances.
Original :
After adding baked texture generated using an algorithm :
Original :
After adding baked texture generated using an algorithm :
Original :
After adding baked texture generated using an algorithm :
Other screens :
The night database I currently have covers almost all of the Europe and some parts of USA.
I stopped the generation process for the moment.
I would love to have your feedback about it !