The Beijing Times has revealed that the fireworks footprint sequence seen by millions of viewers tuning in from all over the world was really computer generated. The 29 fireworks footprints were all actually lit one second apart and progressed all the way from Tiananmen Square to the Bird's Nest stadium. As it turns out, only the last one was filmed for real.
The visual effects department for the opening ceremony felt that the CG sequence had to be inserted because they thought filming all 29 footprints from the air would be next to impossible. The helicopter would have great difficulty getting the right camera angle whilst moving along the route.
Gao Xiaolong, the head of the department reportedly said it took them almost a year to create that sub-minute sequence. Attention to detail included simulating Beijing's night time smog and a slight camera shake as if the sequence was actually filmed from a helicopter.