The animation swoops and swirls like nothing you’ve seen before. Parts of it twist your vision like Escher gone wild. Sometimes it feels like you’re rattling around in the fever-dreaming brain of the animator. It’s glorious.

We’re referring to sequences from “The Thief and The Cobbler,” the never-finished film that master animator Richard Williams began working on in 1964.

Leading a devoted crew including some of the greatest “classical” 2D animators who ever drew, Williams referred to his masterpiece-in-progress as his “mammoth ego trip,” pursuing perfection right up to the day in May 1992, when Warner Bros. shut production down.

The Canadian-born Williams, who made a fortune in commercials and won Oscars for animating “A Christmas Carol” (1971) and “Who Framed Roger Rabbit?” (1988), does not appear in Kevin Schreck’s superb documentary about him and his decades-long project. He won’t discuss it, but Schreck interviews most of the animators who worked on “Thief.”

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What emerges is a surprisingly suspenseful portrait of a kind yet obsessive artist driven to exhausting extremes.

Williams is the Orson Welles of animators, a man who works best when given sufficient funding and total control. When he lost “Thief,” it was poorly finished by others and released theatrically as “Arabian Knight” in 1993. It bombed.

Through interviews and excerpts, Schreck gets us closer to the masterpiece that might’ve been. You sense that a classic work of art has been lost to the vagaries of commerce.

And yet, perhaps all is not lost: Williams, now 80, continues to work on his latest project, promising that “it’s unlike anything anybody’s done.”