Not sure, no one seems to have posted this though it is a little older (06/27/09) but its still a really good read regarding the CGI and what it took.
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Here are a couple snippets;
That effort took hundreds of artists, thousands of hours and even caused one computer to explode.
"We lost some machinery," visual effects supervisor Scott Farrar said with a smile. "The thing just kind of gave up."
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All that's there, Farrar said, are window-washing poles stretched up to 30 feet high. The actors talk to the poles and must react as though giant robots are responding.
"The actors do have to sell it," he said. "It would be a hoot to show what the sequence looks like with the actors talking back and forth but with nothing there other than a couple of sticks and poles."
Maybe on the DVD, he joked.
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More than 350 ILM artists worked on the movie, he said, and they developed new technology to add realism to the robots' design and emotions.
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