I still remember seeing “Lifeforce” in a theater in June 1985 and thinking, “What just happened?”

The movie – which opened the same weekend as sci-fi hit “Cocoon” and was quickly overshadowed by the triple threat of warm and fuzzy feelings, Steve Guttenberg and Wilford Brimley – was one of the most offbeat big-screen releases of the year.

As I rewatched it again 29 years later, I was struck by a number of thoughts. Chief among them was what an oddball resume director Tobe Hooper had: “Texas Chainsaw Massacre,” the Steven Spielberg-produced “Poltergeist” and this.

I was also struck by how few movies featured a character who was frequently nude throughout. Casual nudity in movies, presented like an aside in the 1970s, was already on its way out by the 1980s. These days you’re more likely to see someone cutting someone’s head off than see a naked woman.

“Lifeforce” was based on a book called “The Space Vampires” and is exactly that. The screenplay, co-written by “Alien” Dan O’Bannon, reminds me greatly of Bram Stoker’s “Dracula.” A ship – in this case, a long-range space shuttle, manned by an American and British crew – returns with all on board dead. A half-crazed escapee from the shuttle (Steve Railsback, bringing some of his Charles Manson subtlety from “Helter Skelter” and “The Stunt Man”) talks about a trio of irresistible vampires the crew found in a spacecraft hidden in the tail of a comet.

Meanwhile, the surviving vampire aliens – led by Mathilda May as a mostly-nude seductress – roam around London, infecting strangers and inhabiting bodies.

To continue the “Dracula” parallels, there’s even an insane asylum scene featuring Patrick Stewart, later to achieve fame as Captain Picard and Professor X.

There’s so much to love about “Lifeforce” if you enjoy the offbeat and oddly humorous:

Stewart says “naughty” as no one else possibly could.

Besides Railsback, the two male leads are right out of a “Doctor Who” adventure: Peter Firth is a no-nonsense British government agent and Frank Finlay is an eccentric, white-haired scientist.

Aubrey Morris plays the Brit home secretary. Morris, best known for “A Clockwork Orange,” cracks me up with his reaction shots, looking from one odd person or event to another and wincing a bit every time. Like in the picture above.

Henry Mancini did the score. Henry Mancini.