The two were roommates at Juilliard, before Reeve became the biggest movie star in the world as Superman at 24, before Williams was Mork from “Mork & Mindy.” It was Williams who cheered up a despondent Reeves, who, at the height of his pain, whispered to his wife, Dana, “Maybe we should let me go.” It was Williams and his second wife, Marsha, who bought the Reeve family a special retrofitted van to get him to an appearance at the Academy Awards 10 months after the accident. Williams joined the board of what would become the Christopher & Dana Reeve Foundation and became a disabilities advocate himself. At Reeve’s funeral, Williams called Reeve his brother and said that Reeve had been a steady rock for Williams, “and I was chaos for him,” but Reeve had loved it.

“I always felt that if Chris was still around, Robin would still be alive,” Glenn Close says in the film, in just one of the moments that may have you catching your breath.

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At that premiere screening, sobs and sniffles echoed constantly throughout the theater. “I lost five pounds from the tears,” said one male audience member, who said he kept having to use the moments when the screen turned to black to discreetly wipe his face. The film, by Ian Bonhôte and Peter Ettedgui (“McQueen” and “Rising Phoenix,” about the Paralympic movement), is still without distribution, but seems certain to find a buyer.

This year marks 20 years since Reeve’s death, at 52 from an infection, and Matthew Reeve, his eldest son, told the audience that it just felt like the right time to do something like this. They thought Bonhôte and Ettedgui could make something that felt more like a narrative, more like poetry — and handed over their archive of home videos. Reeve had three children. Two, Matthew and Alexandra, were largely raised in England after he separated from partner Gae Exton, a former modeling agent he’d never married. His youngest, Will, was born after he met his wife, Dana, an actor and singer who devoted herself entirely to Christopher’s care, as well as their advocacy work, after the accident.

All three children give raw and vulnerable interviews, as does Exton; Dana died of lung cancer just 18 months after her husband. “From that moment,” Will says in the film, “I’ve been alone.”

Unlike “Still: A Michael J. Fox Movie,” two of the film’s main subjects, Christopher and Dana, aren’t around to speak for themselves, so the filmmakers use narration from interviews, as well as the audio from Christopher’s post-accident memoir, “Still Me.” Will also reads from his mother’s journals, something he does every March, the month of her birthday and also her death. “It’s nice to get a window into what she was going through in a really trying time,” he told the audience.

This isn’t a conventional documentary, but in many ways a meditation on life, with a structure that jumps back and forth in time from Christopher’s heady days playing Superman to his final nine years in the wheelchair. Throughout are artistic flourishes, like a computer-generated bronze statue of Reeve that develops cracks and starts sprouting what look like shards of green glass after the accident as his body deteriorates. But the film also delves into the controversy that arose in the disabled community around Reeve’s push for a cure, to get out of the chair. It’s because of that outcry that the foundation now has two branches: Today’s Care and Tomorrow’s Cure.

“I’m glad that they showed the some of the backlash from the disabled community, because I feel that, too, the cry of people to say, ‘Love me for who I am and how I am. I’m not going to walk again,’” said Stephani Victor, a four-time Paralympic medalist in Alpine skiing, who loved the movie and was the only member of the audience in a wheelchair. She had been moved to tears telling the Reeve kids how much their father meant to her; she had the car accident that cost her both her legs just six months after Reeve’s accident, and friends had given her his memoir as she recovered in the hospital. Reading it, she said, made her follow her dreams to become an athlete. She also got to meet Williams numerous times when he’d stay all day at the annual fundraiser triathlon for the Challenged Athletes Foundation. “Robin didn’t just show up. He participated in every triathlon,” she said.

It was only after the accident, the film suggests, that Reeve truly went from playing a superhero to becoming one himself, as a parent and as the leader of a foundation that is now a lifeline to 300 million people living with disabilities. “It’s really a film, for us, about family and love, at its core,” said Bonhôte.

Outside the theater, the Reeves were happy to reflect on what Williams and their father had meant to one another. “Their friendship was a beautiful thing,” said Will. “They complemented each other so well, and they were two young kids with a passion for their craft who found each other and then found wild success and stayed true to who they were.”