Spare a thought for the young soldiers in the new film from Ang Lee, who return from Iraq to discover there is no place like home. They’re dropped inside a football stadium, paraded as half-time entertainment, and ordered to dance in formation behind Destiny’s Child. The soldiers are spooked and jittery, like unstable ordnance. When the stage sprays dry ice, one kid flips out and knocks his chaperone on her back.

Lee reckons he can relate to that – at least up to a point. He was raised in Taiwan and moved to the US in his 20s. He finds himself with a foot in two cultures, not quite belonging to either. “I always feel like an outsider looking in,” he says with a laugh. “Those soldiers are the half-time show? That’s just an exaggerated version of how I feel every day.”

Appropriately enough, I meet the director in limbo: in the third-floor suite of a London hotel, with bottled water on the table and seat cushions plumped in readiness. He’s exhausted and jetlagged, midway through his own tour of duty, plugging his product to the four corners of the Earth. Somewhere along the way, Lee’s voice has turned soft and his smile grown tired. Nobody would mistake the man for a soldier. He’s more like an overworked academic, patiently keeping his students in line.

As it happens, Lee’s father was an academic: a school headmaster turned university professor. Lee Sr wanted his son to follow the same path and despaired of his artistic ambitions. He saw the boy as a dreamer, a failure, and appears to have clung to this judgment despite mounting evidence to the contrary. Away in the real world, Lee was forging a fiercely impressive film-making career. He cracked the English-language market with Sense and Sensibility and The Ice Storm. He broke foreign-language box-office records with 2000’s Crouching Tiger, Hidden Dragon. And he won an Oscar for 2005’s heart-piercing Brokeback Mountain (a second, for Life of Pi, would follow in 2012). Yet none of this cut much ice with his dad back in Taiwan.

“My father,” sighs Lee, almost tickled by the memory. “I worked so hard to prove he was wrong. And I did it in every way I knew. Winning an Oscar, making a living, making money. I don’t even think [his disapproval] was because he didn’t like movies. It was more that he thought film-makers were funny people, entertainers, that they didn’t lead a normal life.” He shakes his head. “Finally I got his blessing, his acceptance, right before he died. But I think that was more because I had kids and was raising a family. That was important to him. It showed him I was normal.”

I’m not sure I’d rank Billy Lynn’s Long Halftime Walk alongside Crouching Tiger or Brokeback Mountain, those soaring masterpieces, but it’s a decent, dogged, ambitious picture. Lee conspires to fold the grubby reality of warfare in with the bright paraphernalia of modern America to the point where the two main locations (Iraqi compound, Texas stadium) become an exploded theatrical set, each as heightened, unreal and treacherous as the other.

Lee’s use of pioneering technology adds another level of strangeness. The frame rate for most pictures is 24 per second. Peter Jackson’s Hobbit franchise turned the frequency up to 48. But Lee has gone the full Spinal Tap, shooting in high definition, 120 frames per second, so that the images unfold in a liquid rush. The aim, he says, is to make cinema more immersive, more akin to a lived experience. The paradox, of course, is that the frame rate is so novel that it calls attention to itself. It took filmgoers a year or two to grow accustomed to the talkies. I’m guessing that, given time, watching 120 frames a second will feel as natural as breathing.

Lee is cautiously confident. “The first time I saw 120 frames was on a military flight simulator. And as soon as I saw it, I thought, ‘Damn.’ It felt as though I had been condemned – that I had to pursue it, that I had to be the first to try it. The rules of the game had changed, there was a new language. But that’s scary as well, the fact that here I am being the guinea pig, so to speak.”

In other respects, he remains rigorously old-school. Before starting production, Lee sent his cast off to boot camp so that they could learn to live, work and bond as soldiers. The director demanded they be away for six weeks. He was eventually haggled down to a fortnight. Lee seems so mild, so kind in person. But I have a sense he can be a sergeant major on the set. He blinks and then laughs. “Oh no,” he says. “I don’t think so, no.”

I last met him nearly 10 years ago, just after he had made the excellent Lust, Caution – an erotic wartime thriller about a virginal student who is sent on a mission to first seduce and then kill a Japanese collaborator. At the time, he told me he’d concealed the exact nature of the sex scenes from his two lead actors (Tang Wei, Tony Leung), keeping them in the dark until “they were on the bed and the camera was there”. Today he insists it wasn’t quite like that: the actors knew what they were getting into.

Even so, doubts remain about this approach. In 2013, the Italian director Bernardo Bertolucci appeared to admit that he and Marlon Brando had concealed their precise intentions from the teenaged Maria Schneider regarding the notorious rape scene in Last Tango in Paris. They didn’t tell the actor about the use of butter as a lubricant – presumably in the dubious pursuit of added authenticity. Does Lee have any sympathy with that way of working?

“Yes,” he says. “I have sympathy. I mean, I read that they did inform [Schneider] that there would be something happening. But of course, it’s how you do it. The problem, too, is that she was 18, 19, which is a little on the younger side.” He pulls a face. “A lot of film-makers do that. It’s not nice. But then I don’t think acting is nice. If you wanna be nice, don’t be an actor.”

Another pause. “I think that for actors, if they like acting, if they want to be challenged, then they want to go there. If I hadn’t sensed that with the two actors in Lust, Caution, I wouldn’t have done it, wouldn’t have gone there, because I am not a pornographic director. The love-making scene in Brokeback Mountain, I never told them what to do. Not because I want to keep the freshness – I’m just too embarrassed! And on Lust, Caution, I was the one who broke down. The two actors, they were OK.”

The way Lee tells it, every film he makes is an extension of him. They represent the life not lived, the adventure not taken. He points out that he has been happily married for decades (his wife, Jane, is a molecular biologist). He has two adult sons, Haan and Mason. “In my marriage, I am docile and loyal. Film-making is my alter ego. I’m the Hulk. I’m the hidden dragon. I’m that girl from Lust, Caution – the good girl gone bad. And I need that to feel alive. The movies possess me. Sometimes I worry that it’s something I’m addicted to.” He shakes his head. “I don’t know. I don’t think so.”

If film-making is such a vital outlet, I wonder how Lee coped during his sparse early years. I’ve read that the director spent the bulk of his 30s unemployed in New York, looking after the kids while his wife went to work. That must have been a frustrating period. Lee shrugs. “Looking back now, I think it was fate. I wasn’t ready. I was a late bloomer. It took me a long time. So for those six, seven years, I grew. I did nothing, but I grew from the inside.”

Suddenly he laughs. “But while I was in it, living those six years, it was very frustrating. I am a person who is no good at anything except directing – and it seemed to me that I couldn’t even do that. So yes, those six years were hard.” Did it make him feel that his father had been right? That he was a dreamer? Lee admits that it did – at the time. But now, in his 60s, he feels more able to understand his dad’s point of view.

“My father thought film-making was not normal, a funny business,” he says. “And I think he was right. It’s play acting. It’s make believe. It’s exploring the unspeakable part of humanity. In eastern philosophy that’s a very dangerous thing.” Lee reaches for his glass of water. “So in that sense, my father was not wrong. I could say that, spiritually, what I do is very fulfilling. But physically, emotionally, it is not healthy at all.”

• Billy Lynn’s Long Halftime Walk is out in the UK on 10 February.