The global television audience of more than three billion people watched in amazement as a series of giant footprints outlined in fireworks proceeded through the night sky from Tiananmen Square to the Bird's Nest stadium - except they were watching a computer animation.

Even the giant television screens within the stadium itself broadcast the fake images.

Stunned viewers thought they were watching the string of fireworks filmed from above by a helicopter.

But in reality they were watching a 3D graphics sequence that took almost a year to produce.

It even included a 'camera shake' to mimic the effect of filming from a helicopter.

The dupe was revealed by China's Beijing Times. Speaking to the paper, the man responsible for the animation said he was pleased with the result.

"Seeing how it worked out, it was still a bit too bright compared to the actual fireworks," Gao Xiaolong told the newspaper.

"But most of the audience thought it was filmed live - so that was mission accomplished."

The designers even added some haziness to simulate the polluted Beijing skyline.

Broadcasters around the world had no choice but to show the footage because it all came from one feed provided by Beijing Olympic Broadcasting - the organisation responsible for filming the games.

The ceremony has also been strongly criticised by architect Ai Weiwei, who helped design the Bird's Nest stadium.

Writing on his blog, Mr Ai described the ceremony as "a recycling of the rubbish of fake classical culture tradition; a sacrilegious visual garbage dump and an insult to the spirit of liberty; low class sound play that's just noise pollution".

He was directly critical of China's ruling communist party, characterising the ceremony as "a showcase of the reincarnation of the Marxist imperialism; the ultimate paragon of an all embracing culture of fascist totalitarianism; an encyclopaedia that encompasses total defeat in intellectual spirit."

Mr Ai helped design the stadium alongside Swiss architect firm, Herzog and de Meuron.

But since then, he has become an outspoken blogger against the Olympics and the Chinese regime. Unusually, he has not been censored by the authorities.

Organiser said that the footprint fireworks were there for real, but thought it unsafe to try to film them - so they recreated them instead.