After making his debut with “A Small Circle of Friends” in 1980, director Rob Cohen has increasingly specialized in pictures with a strong action component—“Dragon: The Bruce Lee Story” (1993), “Daylight” (1996), “Dragonheart” (1996), “The Skulls” (2000). But in his last two movies, “The Fast and the Furious” (2001) and “XXX” (2002), he’s taken the genre to new levels. As Cohen put it in a recent Dallas interview, “As you know from my past two films, I’ve been trying to experiment with the actual production of adrenaline and other neuro-transmitters in your brain when you watch a film, so that the film is not just a passive act. I’m trying to make you go ‘Whoop!’ And it’s been a bunch of exploration to take a scene like the drag-racing scene in ‘Fast’ or the avalanche sequence in ‘XXX’ and say, okay, here’s a perceptual way of seeing speed, not just a documentary way.” That’s why he was immediately drawn to the script of “Stealth,” about cutting-edge supersonic military aircraft, the people who fly them, and the possibility that pilots could eventually be replaced by devices with artificial intelligence that may–or may not–work as their makers intend.

W.D. Richter’s script “came from the producers, Laura Ziskin and Mike Medavoy,” Cohen said. “I’d just finished releasing ‘XXX’ and we were enjoying that success. And I looked at it and I went, well, for a science-fiction movie this is really cool, because nothing moves faster on earth than these jets. And I thought, let me look into this. And when I got on the Web and found out that these UCAVs [Unmanned Combat Aerial Vehicles] were literally on-line and being experimented with, I went, ‘Oh, boy! Here’s a new dimension–this idea of warfare at remote, either by the joystick approach (which is what they’re trying to tell the public), but the fact is–I know for sure–they have full AI, not talking, thinking computers but computers that basically know how to take an airplane off a base, identify a pre-programmed target, shoot a missile and then return to base. This is a new development, like a fifth industrial revolution. The combination of visual effects challenge and substance of historical moment seemed pretty heady and challenging. So I said yes.”

Cohen talked at length about the technological demands of the film. “In ‘Top Gun,’” he said of the classic fighter-plane movie of 1986, “the most advanced thing Tony Scott did was to find a way to strap a mount on the Tomcat. When you make a movie like this, you say, well, that movie did it as well [as it could] in that time, but what can I do today?” Returning to the distinction between a “perceptual” as opposed to “documentary” mode of perceiving speed, he went on, “I would call ‘Top Gun’ a documentary way–okay, here’s the real world, and we have jets in it and we figure out ways to film them. First of all, I want to do jets that are not in the real world. Let’s see where it will go. So I went to Northrup Aviation [and] got with the head designers at Northrup, and I said, ‘Where’s it going? Where can it go in hypersonic jets?’ So we started to look at the script and started to design what they call switchblade technology, the scissoring wings, swing wings, the stealth profile, the pulse-detonation engines, the sonic-jet technology–all of which were on the drawing boards. Three years later, they’re doing it. In my own time they went from ‘Impossible!’ to ‘They’re doing it!’”

But what was imagined on the drawing-boards also had to be rendered convincingly on film. And here Cohen turned to the techniques he’d used in his previous films, but on a much larger scale. “What I learned in ‘XXX,’” he said, “in the avalanche, is that I actually could take a real earth-bound event and film it in the computer’s mind the way it would be impossible to film [in reality]. You can’t put people in jeopardy–you can’t do that. Using particle animation, I could in fact create this experience of this situation, impossible to film or even to happen. But it means we’re going to have to solve several major challenges. One is, we know this earth. This isn’t a galaxy far, far away, this isn’t the planet of the talking crystals. This is earth, and we have a sense of what light and physics do on this earth, and if anything is wrong, we also can spot it quickly—‘Oh, that’s CG.’ We know that now. There’s a thousand clues about light reflection and depth perception–thousands of clues within each shot where where we register why we believe what’s happening, or why we don’t, from our own experience. So we’re going to have to commit to 838–that’s what it turned out to be, 838–visual effects shots, in which every one of them has to be photo-real. I have to have our advanced jets landing on our present-day carriers, and you have to go, ‘Absolutely.’ That was really daunting.”

Second, Cohen said, “I had this idea of effecting total camera freedom in space and at these speeds. And it was, again, impossible to do it for real. There’s no camera mounting system that can do that. So the background in this world that we know had to be computer-generated. You can’t change the perspectives by any other means except a total commitment to the CG world.” That led to the development of a software program that came to be called Tergen, or Terrain Generator, which, when combined with a 100-ton gimbal, a device that allows the jet to incline at different angles in all directions, simulating a flight path actually controlled by Navy pilot (“It moved the actor in exactly the way the situation called for,” Cohen explained), completed the illusion. “Most of what you see in the film, in terms of the world, is not plates. There are some plates, because there are some things it was easy to make plates of. But I would say 80% of everything they’re flying over–and 47½ minutes of the picture–is pure visual effects. 80% of that is also generated by the computer.”

The third major requirement, Cohen said, was the need to replicate the appearance of glass, which couldn’t actually be used in the shots. “We’ve got to figure out how to make digital glass for every shot,” he recalled of the challenge. “And we did. Between the environment, the glass, and the actual camera freedom, we did things in this picture that make ‘Top Gun’”–a film he much admires–“look like it was quite another era.”

The director reflected on the technological side of “Stealth” (and his other films) and said, “This is the fun part of visual effects. It makes you observe the real world [more closely]. When you question why some of this stuff feels real, it’s because of that kind of [attention to] detail.”

But even the most effects-laden movie still needs actors, and here “Stealth” pulls a surprise by casting Sam Shepard as the captain in charge of the UCAV program, who turns out to be not nearly as noble as one might expect. Cohen admitted that he cast Shepard because of his performance as Chuck Yeager in another classic film about flight, Philip Kaufman’s “The Right Stuff” (1983). “I wanted Sam because you’ve got Joe Morton, who’s Mr. Sky Net [and who here plays the officer doubtful about unmanned jets] and you’ve got Sam Shepard, who’s Mr. ‘Right Stuff,’ [and] well, what if they traded places? I thought it would be a fun movie archetype flip. There’s no doubt in my mind that Sam Shepard is an extraordinary American icon, and I wanted him to play the darkness that he writes about in his plays, as opposed to the ‘Yup, sure, nope’–you know, he’s so great and Gary Cooperish in his movies. I said, who wrote these plays? Not that guy–that guy wouldn’t spend any time thinking about the darkness in the American landscape. There must be a reason he writes these plays. And I read a book of short stories by him, and some of it was horrifying–his relationship in the book with his father. I said, your father was a tough guy, and he said, ‘Yeah.’ And I say, ‘Then play your father.’ And he did. He put a real tragic quality in this guy.”