Now a major player on the international art scene, Ai Weiwei was little known in his homeland until May 2008, when 70,000 people died in an earthquake in Sichuan province. Outraged by the Chinese government's apparent indifference to the tragedy, Ai began to collect the names of dead children and to document the shoddy "tofu" construction that led to the collapse of thousands of buildings, especially schools. Volunteers helped him compile the names of 5,212 children who died. Later he made a huge mural in Munich, Germany, composed of colorful backpacks like those the children left behind.

By the time American filmmaker Alison Klayman began following him in December of that year, Ai was emerging as a political activist and cultural provocateur. In her intriguing film "Never Sorry," she interviews him at his spacious, ultra-modern home in Beijing, then follows him through the ruins of Sichuan, to confrontations with officials in Chinese police stations, and eventually to museums in Munich and London where he's greeted like a superstar.

At the Tate Modern in London he spread 100 million hand-painted porcelain sunflower seeds across the floor. Beautiful and strange, the seeds are a striking metaphor for China's history as the inventor of porcelain and its reputation as an industrial powerhouse whose success is grounded in its immense population and central planning. Where but China could such a project be produced? And what would happen if every Chinese "seed" realized its individual potential? That, in the end, seems to be Ai's goal -- to stir his compatriots to action.

The nonlinear film is an inviting jumble of incidents, interviews and ruminations in which we meet Ai and his family (mother, brother, wife, mistress and 18 month-old son), his art dealers and supporters, and his international followers.

The son of a Communist poet, Ai was born in Beijing in 1957 but grew up in the provinces, where his family was exiled after falling into disfavor with Chairman Mao. After Mao's death in 1976, Ai returned to Beijing and began studying film. He lived in the United States, mostly in New York, from 1981 to 1993. He perfected his English, began exhibiting his art, and formed a passion for American-style democracy with all its messy candor and contradictions.

Back in China, he published underground books about such Western artists as Andy Warhol and Jeff Koons. Gradually his own art became more political and confrontational, including films and photos in which he throws juvenile insults at the Chinese motherland, raising his middle finger and shouting "f--- off." Harassed and beaten at one point, he insists on pressing charges that he and his lawyer admit won't change anything.

Affable and unpretentious, Ai comes across as a cagey operator whose candor is very appealing. At first he publicizes his activities on a popular blog, but after Chinese officials shut that down, he turns to Twitter.

In January 2011 his new studio was bulldozed by the government. In April he was arrested and disappeared for 81 days, prompting an international outcry including a plea for his release by Secretary of State Hillary Rodham Clinton. Once free, he was hit with a $2.4 million tax bill. Within 24 hours, his followers contributed more than 1 million Chinese yen to his cause, sometimes folding bills into paper airplanes and sailing them over the walls of his Beijing home.

"I think it is a responsibility for any artist to protect freedom of expression," he says, adding a Sarah Palinesque footnote: "Never retreat; retweet."

Mary Abbe • 612-673-4431