When Stanley Kubrick’s “2001: A Space Odyssey” opened in April 1968, few in the audience understood it, though most would never admit it. All they knew was they had just seen something like they had never seen before.

The Cannes Film Festival will celebrate the 50th anniversary of “2001: A Space Odyssey” with the world premiere of an unrestored 70mm print, introduced by Christopher Nolan, May 12.

Filmmaker James Cameron was no different. At age 14, he took the film in at the Castle Theatre in Toronto — where, as in many cities, it played continuously for two years. “The word used to describe it was ‘mindblowing,’” he recalls. “It was like no cinematic journey like I’d ever seen before.”

Kubrick’s space epic hurled science fiction films far beyond the edges of the galaxy that they had inhabited up to that time. It brought a massive shift in sci-fi storytelling, as well as the way in which visual effects were not only created, but the way filmmakers used them.

“It made science fiction a first class genre,” Cameron says. Sci- fi movies up until then tended to be pigeonholed, he notes, “just your monsters and your space ships.” Even attempts to elevate it, like 1951’s “The Day the Earth Stood Still” and 1956’s “Forbidden Planet” never really pushed it out of that world. But “2001” was different. “ ‘2001’ burst through that. It took it to the level of world class, important, profound, philosophical, artistic filmmaking. It also asked big, profound questions, about human origins and the nature of man and the universe, and where we’re going,” says Cameron.

“It was the first time that science fiction was really treated in a serious manner,” says Industrial Light and Magic’s chief creative officer and Oscar-winning visual effects supervisor John Knoll. “Prior to that, sci-fi films were typically campy or schlocky. This film had thought-provoking themes and extremely high-quality execution.”

Kubrick and science fiction author Arthur C. Clarke had seen an eye-catching 70mm film in a domed theater at the New York World’s Fair in 1965, called “To the Moon and Beyond,” which was created by Hollywood-based Graphic Film, where a 23-year-old graphic artist, Douglas Trumbull, was working. “They made a wide range of space movies, mostly for NASA and the air force,” Trumbull recalls. Kubrick hired Graphic to do preliminary design studies for his and Clarke’s film, then titled “Journey Beyond the Stars.” The director eventually moved the production to England, with Trumbull coming as an animator, and his boss at Graphic, Con Pederson, arriving not long after. Wally Veevers, who had worked on “Universe,” a film for the National Film Board of Canada that Kubrick had seen, was also brought onboard.

One of the most important elements of Kubrick’s approach to the film (which was based on Clarke’s short story “The Sentinel”) was one of realism — a sure break from sci-fi films of the past. “Arthur had a long history as a very scientifically oriented science fiction writer,” Trumbull explains. “He didn’t write about fanciful things, he wrote about real science, real technology” — something that had great appeal to Kubrick. “The whole project was suffused with a determination to make everything look believable.”

To accomplish this, Clarke and Kubrick brought in consultants both from space agencies and industry to advise on things like spacecraft design, computer display and control design (courtesy of IBM). Kubrick also hired Harry Lange, a spacecraft designer for rocket builder Wernher von Braun, and spacecraft designer Frederick Ordway. “Harry Lange was a true spacecraft designer,” says Trumbull. “He knew all about ballistics, orbital mechanics, rocket fuel and rocket nozzles. So he brought to the movie a tremendous accuracy and verisimilitude to real spacecraft possibilities.”

“Everything in ‘2001’ felt purpose-built,” says Weta Digital’s Oscar-winning senior visual effects supervisor Joe Letteri. “It had a scientific and an engineering basis.”

The Discovery, the colossal ship on which the astronauts travel to Jupiter, was nowhere near the silly or fanciful “rocket ships” of the past. “Prior to that, what you saw in space science-fiction films were more like adaptations of either airplanes or flying saucers. None of them looked like true space vehicles,” says Letteri.

Cameron agrees. “Hollywood had always done aerodynamic spacecraft, whether it was a flying saucer, with a smooth surface, or a pointy-tipped rocket ship with 1930s tail fins straight out of ‘Buck Rogers.’ Kubrick said, ‘If there’s no medium, no air, then things don’t need to be aerodynamic.’”

Discovery’s design, built in space and never touching Earth’s atmosphere, was functional — 200 yards long, with a lengthy truss separating the plasma-powered engines from the globe housing the human inhabitants. And its model was decorated with pieces from World War II aircraft parts from plastic model kits to add to the realistic look. “That became the order of the day, thereafter,” adds Trumbull.

The models were photographed in a way not ever employed before. “Kubrick wanted to create crisp and clear images of the spacecraft,” Trumbull explains, with no motion blur. The team eventually settled on extremely long exposures, with f22.0 stops, over several seconds per frame — and something else: essentially, the first motion control system.

Developed by Wally Veevers, the system used AC Synchronous motors on fixed track to move the cameras very slowly along a fixed track. Says Knoll, “It moved the camera 1/16 of an inch per second. [Trumball] has described it as like watching the hour hand of a clock. But it gave great depth of field and high realism,” as did Kubrick’s lighting. “The way those ships were lit established the look of how you would light space ships there on out,” notes Letteri. “They invented that vocabulary for us.”

Adds Oscar-winning visual effects supervisor Rob Legato, “The quality and caliber of the model, and the way it’s photographed and lit, combine to make something that can fool your eye. Otherwise, if you detect it onscreen, it belies that it was a model.”

Kubrick’s sound design for them also made it realistic — in many cases, there is none, just silence. Notes Cameron, “Kubrick was bothered by the fact that film had never adequately showed that there’s no sound in space. When you’re in a vacuum, you wouldn’t hear sound effects. He embraced that, he leaned into it, in a way that was disturbing and made you think.”

The shooting style, via DP Geoffrey Unsworth, as well as the performances, also added to the realistic experience of such a journey for the audience. “That was a very conscious effort on Kubrick’s part to strip away the trappings of normal cinematic melodrama,” Trumbull says. “He wanted just the opposite. He wanted the audience to feel that they were in space themselves, and have that experience — to make it immersive. He didn’t want the usual over-the-shoulder or reverse shots. He told me, ‘I want the audience to feel like they’re actually on this adventure themselves.’ There are no shouts of ‘Oh, my God — we’re entering the Stargate! What do we now?’ In this film, things just happen.”

In fact, the astronauts, Bowman and Poole (Keir Dullea and Gary Lockwood), have a dullness to their personalities, reflecting a sense of desolation and boredom. “Kubrick gave you the sense of time of a long mission,” says Cameron. “’This is what it looks like on Day 480: I get up, scratch myself, go for a little run, get a recorded message from my parents because it’s my birthday, which I forgot, because I’m so detached from the reality of Earth.” Adds Letteri, “They’ve committed themselves to two years of their lives or longer, to make that trip. And Kubrick doesn’t downplay it. There’s no quick jumps through the space-time continuum to get you there faster. This is what it takes.” The astronauts speak not much different from the Mission Control communications they get from Earth, not like some heroic, fictional heroes, Legato points out. “There was a whole code of ethic, this incredible calm, taking everything in a very serene way, even if you’re under tremendous duress. They underplay whatever’s happening, as pilots do.”

Another voice is far different from any of its predecessors — that of the Discovery’s onboard computer, the HAL 9000, known simply as “HAL.” Unlike the robots of yesteryear, (before “2001”), HAL is not bipedal and doesn’t move jerkily, it doesn’t talk with a mechanical voice. In other words, he ain’t Robby the Robot.

In fact, HAL is only seen as red lenses scattered about the ship, and gently voiced by actor Douglas Rains (who replaced Kubrick’s initial choice, Martin Balsam), the actor who narrated “Universe.” “He is an A.I. (artificial intelligence) that manages the vast complexities of the ship, adjusting the temperature on this, the pressure of that, separate from the astronauts, so that they can deal with more high-level things,” Knoll explains.

But he is more than that. “People talk about A.I. and about robots, as if they’re separate things,” explains Cameron. “In reality, one is embodied and one is not. But this disembodied A.I. has an almost godlike or spiritual quality, because it doesn’t have a body — it’s just a voice. That hadn’t been seen before ‘2001.’ And that put it on a different level.”

Bowman and Poole have a relationship with HAL — he is not simply given orders. “By taking the man-in-the-suit out of it, now you’re dealing with an intelligence that isn’t biological, isn’t in any way human, but is intelligent.”

His intelligence eventually leads him to determine that, to protect the mission, he must kill the astronauts, including those lying in hibernation — a story decision that came late in the process, Trumbull notes. “There had been IBM logos on everything, but when IBM heard about that, they removed their logos — they didn’t want to be associated with a robot that murders people!” And though the letters “HAL” are indeed each one letter off from “IBM,” Trumbull notes that was indeed a coincidence. “Arthur Clarke was vehement about that. He had invented the term Heuristic Algorithmic computer — HAL.”

Among Trumbull’s biggest challenges came in the form of the Stargate — the momentous end sequence where the aliens advance Bowman by transforming him into a “star child,” before sending him back to Earth to keep track of human activity. As written in the screenplay, he notes, the gate was a slot in one of Jupiter’s moons, through which one could enter another universe. “We could not figure out how in hell to depict that,” he recalls.

Trumbull, though, remembered a technique he had seen created by futurist animator John Whitney, in “To the Moon and Beyond,” which perhaps could be adapted for this purpose. The method, which Trumbull dubbed “slit can,” utilized art on an animation stand covered, except for a horizontal slit, and photographed with a 65mm camera aimed down at it with its shutter open on a single frame, while the camera was moved downward toward the art; this was then repeated with the art moved slightly and shot on the next frame. “By moving the camera toward it, you could, essentially create a corridor of light,” eventually becoming a sequence unlike any ever produced on film, which flat out left audiences breathless.

During the time of its release, in mid-1968, there were, of course, audience members who came to see “2001,” not to get a good dose of science fiction, but to take advantage of the effects of the dose of whatever they had just ingested. “I had never thought of the Stargate as a light show or something hallucinogenic,” Trumbull says. “We just did what we thought served the story.” It was not, however, lost on a studio executive, who, noting who the returning audience members were, added “The Ultimate Trip” to the film’s theatrical posters and marketing.

The advances in visual effects 2001 represented were not lost on Kubrick when he created the film’s end credit sequence, prominently introducing credits for the four “Special Photographic Effects Supervisors,” today known as Visual Effects Supervisors — Trumbull, Veevers, Pederson and Tom Howard. Prior to “2001,” such pioneers as John P. Fulton and L.B. Abbott were simply credited for “Special Effects,” a term now used to refer to practical/physical effects on set. [King Kong’s creator, Willis O’Brien, in 1933, received simply the credit of “Technician”]. Sadly, the Academy, at the time, would only accommodate up to three names in a nomination for an Oscar for such a category – so Kubrick took home the statuette himself. “I always felt that belonged to all of us,” Trumbull notes.

The effect of “2001” on future sci-fi storytellers has been immeasurable, each one learning from the generation before. “Everybody from Steven Spielberg, Jim Cameron, George Lucas to Michael Bay, and now the following generation, people like Christopher Nolan, fully embraced what Stanley did,” says Legato. ”Kubrick really changed a lot of thinking, and allowed the next generation of filmmakers to tell the kind of stories they want and the way they want. What we’ve all learned from him is that once you know it’s achievable, then you can go out and try to achieve it yourself. Because this mindblowing movie, this epic, transcended the artform and became an artform.”