I spent a bit of time working to make each apartment unit and the sheets of fabric look unique, so there would not be a very discernible pattern in the textures, colors, and motion. Then, while trying to add an atmospheric effect to emulate heavy pollution, I accidentally got this blurred effect, I found I quite liked it - though the effect does obliterate much of the detail I worked so hard to incorporate. Particularly ironic, since I spent a ton of time getting the fabric sheets to blow in the wind in a non-uniform way. Let me tell you, rendering a couple of hundred moving pieces of fabric on an image this size is no small chore, even on a relatively beefed up computer.

 

Still, I am glad for all the work, as I learned a couple of new techniques I can use down the road. I may even be able to reuse the apartment blocks again.

 

There are 78 apartment units between the two towers and about 546 fabric sheets - though you cannot see them all. Part of the process was to create 7 pieces of fabric hanging on the railing of each apartment, but with a material that not only had random hue, saturation and value, but with a randomized visibility. That was to save me the trouble of having to manually place each one so it looked random.

Here is a quick render of one of the units and some of the fabric...

This is the layout of the scene in blender. The wireframe planes are the atmospheric effects - which turned out to be more of a blurring effect...

... and the final image, after post-processing.