The sci-fi epic “Dune” boasts a few films’ worth of giant sandworms, amazing spaceships, cosmic armies and galactic political drama, though it essentially is only half a movie.

Director Denis Villeneuve’s visually arresting big-budget adaptation of Frank Herbert’s classic – well, a good bit of the novel anyway – is an odd bird and a mixed bag. “Dune” (★★½ out of four; rated PG-13; in theaters and on HBO Max Thursday) is impressively ambitious in scale, like Villeneuve mashing up the worlds of “Star Wars” and “Game of Thrones,” but with that unmistakable signature style he showcased with “Arrival” and “Blade Runner 2049.”

While the film (currently playing the film-festival circuit, hopping from Venice to Toronto to New York) has a lot going for it, including a pretty stellar cast, real-world metaphors and an intriguing twist on a war-movie aesthetic, it’s lacking in character development, and aspects of the book’s substantial mythology are tossed in to keep your head swimming over 2½ hours.