Spike Jonze's 'Her' an original take on a future L.A

In "Spike Jonze's 'Her' a refreshingly original take on a future L.A." by Christopher Hawthorne, he talks about how the filmmakers created a futuristic L.A. but it does not look utopian or dystopian. The style looks like our current era. "Jonze and his production designer, K.K. Barrett, digitally plumped up the city's existing skyline," explains Hawthorne. He even states that Jonze was talking with New York architect Elizabeth Diller, whose firm is designing Eli Broad's new contemporary art museum in downtown Los Angeles. Filmmakers also shot some scenes in Shanghai's Pundong district because of the new skyscrapers and so his actors won't worry if the cars looked futuristic.
I haven't seen this film yet but what caught my eye is that the director didn't want to make the futuristic L.A. look utopian or dystopian, it seems like he wanted to make it look like this era. I liked that because technology is always improving but sometimes the architecture  isn't changing that much. 
An impact that can have on film students is teaching them how to create a world of their own for their films. They could use that to experiment and once they have the knowledge of doing that, they can use it for long run. 
My questions: What type of software or thing did they use to create that futuristic (but not utopian or dystopian) L.A? How did they plump the city's existing skyline? http://www.latimes.com/entertainment/news/arts/la-et-cm-her-architecture-notebook,0,7810736.story#axzz2rHy5qYhu