While the dramatic display actually happened as portrayed on television, members of the Beijing Olympic Committee said it was necessary to replace live video with computer-generated imagery because the city’s hazy, smoggy skies made it too difficult to see, according to The Beijing Times, which first reported the story.
Committee members also said they were concerned that the helicopter pilot who would have flown overhead to film the fireworks would have been “at risk by making him try to follow the firework route,” according to a quote from a committee member reported in a Daily Telegraph story.
NBC broadcasters Matt Lauer and Bob Costas made mention of the alteration as it aired.
"You’re looking at a cinematic device employed by Zhang Yimou here," Lauer said. "This is actually almost animation. A footstep a second, 29 in all, to signify the 29 Olympiads."
Costas responded, "We said earlier that aspects of this Opening Ceremony are almost like cinema in real time. Well this is quite literally cinematic."
I heard that last exchange by Lauer and Costas, but I thought they were just being coy, since most viewers wouldn't have even heard of Zhang Yimou or his day job.