"The Great Buster," a new documentary about the silent-film star Buster Keaton, arises out of a lifelong love affair.

"My father took me to see him at the Museum of Modern Art when I was about 6 or 7 years old, or maybe 5 — I don't know, pretty young," said Peter Bogdanovich, the film's director.

Bogdanovich, in his late 70s now, directed such movie classics as "The Last Picture Show," "Paper Moon" and "What's Up, Doc?" He's also a critic and film historian with a string of documentaries to his name. When William Cohen, who owns the rights to all the Keaton films of the 1920s, approached him about making a Keaton documentary, he said yes immediately.

Buster Keaton not only created some of the great movies of the '20s; he also developed the foundation of comedic film as we know it today. Bogdanovich's film explores that legacy.

Making silent films involves a certain approach to storytelling. Bogdanovich said the silents represent the golden age of film comedy.

Director Peter Bogdanovich is known for his feature work, but also as a critic and film historian. He says he jumped at the chance to make a film celebrating Buster Keaton. Courtesy Cohen Media Group

"Because it was black and white, which is not distracting, and you didn't have to wait for laughs, because there was no dialogue," he said. "It was a great period for comedy, and Buster was maybe the funniest of them all."

Like many silent stars, Keaton came out of vaudeville. His parents did a comedy act. In the film, Keaton's friend Dick Van Dyke says they quickly involved their son in their slapstick routine in an alarming way.

"They had a handle on him, like a suitcase, and they used to throw him around the stage," he said. Supposedly, Keaton's father even threw him at a heckler one night.

Not surprisingly, the older Keatons were repeatedly arrested for child abuse, but were always able to prove it was all an illusion. They taught Buster at an early age how to take a fall, a skill that he used all the way through his film career. Bogdanovich said he even got his name "Buster" from his falling ability.

"Supposedly Harry Houdini saw him fall down a flight of stairs when he was like a year old or less, and said, 'That was some buster your kid took.' 'Buster' meaning a fall in those days. And that name stuck," Bogdanovich said.

As an adult, Keaton felt the attraction of a new medium, moving pictures. It drew him to California at the birth of the Hollywood film industry. He made two-reelers, short comedic films. Movie theaters of the time would play several during a performance.

Keaton was famed for his elaborate stunts, involving steam trains and falling houses. Bogdanovich said Keaton always did them himself.

Buster Keaton in "The General." Seen by film historians as one of his best works and one of the great films of all time, the movie upset some critics when it came out in 1926 because of the way it treated the Civil War. Courtesy Cohen Media Group

"I don't know how he did it," he said. "Some of those falls are extraordinary."

He was also famous for his lack of expression, and became known as the Great Stone Face.

"He just didn't smile, or laugh," said Bogdanovich. "He was too busy being funny."

"The Great Buster" includes a number of current filmmakers describing how that lack of a smile does not mean a lack of expression. His used his eyes. Jon Watts faced a similar challenge when directing 2017's "Spiderman Homecoming" during the scenes when Peter Parker dons his Spidey mask.

"Here I have this character who has almost no expression in his face, but there is so much personality you want to create, and so much humor you want to bring out in the physicality. So I just went back and watched a bunch of Buster Keaton films," Watts said. "I used that as a baseline for so many 'Spiderman' moments."

"The Great Buster" shows Keaton's rise to fame and then his fall, when he was chewed up by the arrival of sound and the studio system. He kept working, though, until his death in 1966, doing bit parts and commercials, even making ads for Minnesota based Northwest Orient airlines.

While he was still alive, Keaton was honored overseas for his work. But Bogdanovich said that wasn't so true in the United States.

"That's America for you," he said. "Gore Vidal called it the United States of Amnesia. We discard, we forget the great work these people do and we move on. It's a young country and we haven't grown up yet."

But one great thing about the modern era, said Bogdanovich, is that all of Keaton's work is still available, on discs or online. You just have to go looking for it.