Done in Photoshop, Softimage, Redshift and After Effects. Textures based on Marc Khachfe's beautiful OhMyMaps images. After extending the illuminated region around the city by several dozen miles in each direction, I developed tools in Softimage ICE to convert the texture data to particle clouds which allowed millions of points of light in each frame.
Using high-resolution stills for backplates, I created subtle animated distortions of the cloud forms. The balloons were created entirely in Maya (except for their live-action passengers) and rendered in Mental Ray. Compositing was done in After Effects.