Cai Guo-qiang is probably best known for designing the 2008 Olympic Games "giant footprints", 29 such-shaped fireworks lighting up the Beijing sky to celebrate the opening ceremony. The spectacle was watched by 2 billion people across the world. But this is not his only claim to fame.

In a semi-biographical documentary film Sky Ladder: The Art of Cai Guo-qiang, the 59-year-old artist reveals his dream project.

In a fishing village nestled in his hometown Quanzhou, in Fujian province, Cai ignites a 500-meter-long ladder made of rope and gunpowder. The ladder shimmers in the sky when it is carried high by a giant hot air balloon.

It's Cai's work Sky Ladder, part of his Projects for Extraterrestrials, which he began in 1990.

Using fireworks, Cai says he wants to explore the links between humankind and the unseen world.

The Sky Ladder work failed three times. It was set to take off from either Bath (United Kingdom), Beijing or Los Angeles (United States), but it was not possible either due to bad weather or security reasons.

"Many people tried to persuade me to quit. But I persisted. It's a tribute to my 100-year-old grandmother," says Cai in Shanghai, where the documentary was screened recently.

For the New York-based artist, the screening was also a chance for his grandmother-the first in his family to believe in his ability-to see his dream project.

On June 15, 2015, the documentary was watched upon its completion by a small group of participants and local villagers.

More than 1,000 people watched it on big screen in a cinema, the first of such screening on the Chinese mainland, at the recent 20th Shanghai International Film Festival.

The production has been streamed on Netflix to around 190 countries since mid-October in 2016.

The documentary, directed by Oscar-winning Kevin Macdonald, traces Cai's journey from his early days in Quanzhou.

Cai says the filming was "amazing yet confusing".

"For quite a long time, Kevin could not figure out how to develop the story. He and his crew followed me for two years, always asking me questions," he says.

Explaining why he picked Macdonald to direct the film, he says: "They (the producers) offered me a list of directors. But Kevin had never been to China and knew very little about me and my art," he says.

"I immediately said I wanted him. I did not want someone to talk too much about my prizes or achievements. I wanted someone to tell my story through the perspective of an ordinary onlooker," says Cai.

The idea of making the documentary came from a chat with Xiong Xiaoge, a renowned investor and founding partner of IDG Capital, during a flight to Russia in 2014.

Xiong, who was impressed by Cai's artworks, later invited two other investors: Chinese-American businesswoman Wendi Deng and Liu Dejian, chairman of the Fujian-based tech firm Netdragon Websoft.

Cai says he is glad to see the documentary being well received online with scores of 7.4 on IMDb and Rotten Tomatoes.

Some of the scenes capture Cai's daily life, such as an emotional conversation with his sick father.

One scene shows his early years playing a villain in a black and white movie.

Speaking about the future, Cai says he will keep painting and producing gunpowder works.

"I feel I have been lucky. I can do what I want to do."