Tom Cruise has long been known as a leading man and action movie hero, but seldom has he been described as a technology pioneer.

Yet that’s the role the actor played on all four “Mission: Impossible” films, said David Dozoretz, senior previsualization supervisor on Paramount’s “Mission: Impossible — Ghost Protocol,” which has cumed more than $141 million domestically and $225 million overseas.

Dodoretz, who worked on three of the pictures (he skipped “M:I2” as he was occupied with the “Star Wars” prequels), said that 1996’s “Mission: Impossible,” which launched the series, “was the first movie that really used previs,” a computer animation program that adds motion and graphics to the storyboard process and allows everyone on a picture — from below-the-line department heads to top studio execs — to get an advance sense of what a scene will look like in order to make informed production decisions.

Dozoretz, who was then with ILM, recalls that on the first “M:I” Cruise and the producers wanted to do a sequence in which a train pulls a helicopter into the Channel Tunnel.

“The studio wasn’t really sure about it, so we all decided to do a rough computer animation to show what it can look like,” said Dozoretz.

Since that early application, which Cruise encouraged, previs has been deployed on hundreds of big-budget movies to aid in the decision-making process and — significantly — to save money.

By the time “M:I4” was in development, Dozoretz had become a previs maven. He’s one of the founders of the Previsualization Society, a trade group, and for the past dozen years has been running Persistence of Vision, a previs consulting shingle.

Dozoretz was working on the J.J. Abrams-directed “Super 8” when he got word that Abrams was was planning to produce the fourth “Mission” installment.

“They didn’t have a script yet, only a rough treatment,” Dozoretz recalled. “One sequence was going to take place on top of the world’s tallest building” — the 160-floor Burj Khalifa in Dubai.

By January 2010, Dozoretz and his team were on board and worked steadily on “M:I4” for the next 12 months.

“It was really early on,” he said. “We were starting on the Burja previs even as J.J. was first talking with (director) Brad (Bird) in the other room.”

Production designer James Bissell recalled that pre-production on “M:I4” was “truncated” as a result of protracted negotiations among the major players behind the film. It took some time before a full script was available, “and then we were on three continents, filming second unit in Moscow and first units in Dubai and Prague, and additional locations in Vancouver.”

Previs, he added, was particularly useful in such pressured circumstances in order to help Bird — who had heretofore only helmed animated pics — visualize difficult and complex live-action sequences.

Bissell and others fed data into the previs computers, helping Dozoretz build several “M:I4” scenes — none more dramatic than the film’s signature sequence, in which Cruise climbs up the Burj Khalifa’s sleek surface 130 stories above the ground, rappelling from floor to floor in order to access a secure computer room from the outside.

More than six months before any shooting took place, Dozoretz created as many as “15 or 20” versions of the sequence for Bird.

“We’d show it to Brad, and he’d say, ‘This isn’t quite working.’?”

Bird would then make suggestions for picking up the pace in some areas, slowing it down in others. Then the team would show the previs sequences to the studio and decide how the shooting would take place.

At that point the previs also got disseminated to most of the film’s department heads. “They’d put the previs on a large monitor and go through whole scenes, one shot at a time,” said Dozoretz, “deciding how they were going to get certain shots, what they need to do at certain points during production and how to rig for safety.”But there was one factor no one could have predicted. “When we spent those first six months working on the sequence, we thought it was all going to be visual effects work,” Dozoretz said. “We figured they’ll shoot plates and Tom will be put in digitally.”

But Cruise had other plans: He wanted to do his own stunts, and to suspend himself in a harness 130 floors above the ground while helicopters flew around and Imax cameras recorded his vertigo-inducing moves up and down the side of the mirrored tower.

“When we were designing the sequence we thought we could do anything because it was going to be all digital,” said Dozoretz, “But it turned out to be the real Tom.”

So instead of creating a virtual world, the vfx artists ended up with the opposite task: They worked on live-action images of Cruise suspended in mid-air and carefully removed wires, cables and reflections of the crew in the building’s exterior.