The Academy Award-winning documentarian Morgan Neville, who took home an Oscar for “20 Feet From Stardom” in 2014, is turning his camera to the Hollywood auteur Orson Welles, focusing on the final 15 years of his life.

The film will serve as a companion piece of sorts to Welles’s final unfinished opus, the satirical “The Other Side of the Wind,” which now appears closer to completion after Netflix stepped in. The streaming service is producing Mr. Neville’s documentary, too.

While the decades-in-the-making “The Other Side of the Wind” is a saga unto itself, Mr. Neville wants to put the film in context by exploring Welles’s struggles in Hollywood as he toiled to complete the movie, which was meant to be his comeback.

Starring John Huston, “The Other Side of the Wind” was filmed in fits and starts in the early to mid-’70s, but its completion was stymied by ownership complications; financial hurdles and a revolution; and Welles’s death in 1985. A major stakeholder was the brother-in-law of the Shah of Iran; after the Iranian revolution, the government attempted to seize the negatives. Until recently, it seemed doomed to join the dozens of other unfinished projects in Welles’s oeuvre.