Ang Lee’s upcoming science fiction action thriller “Gemini Man” had been languishing in Hollywood development for more than two decades. But thanks to modern moviemaking technology, the film, which wrapped production in July, is finally seeing the light of day. And star Mary Elizabeth Winstead told us it could change how audiences watch movies altogether.

Winstead caught up with TheWrap over the phone while promoting her new film “All About Nina,” and talked about working with “the most wonderful person,” Will Smith, and what audiences can expect from “Gemini Man.”

“We started in February, so it was a long project, but it was really amazing,” Winstead said of filming. “It’s this big action movie, but with a heart. You know with Ang Lee directing you’re going to have some thoughtfulness behind it. Really it was a wonderful thing to be a part of.”

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Winstead stars opposite Smith as an operative tasked with surveilling Smith’s character. The film follows an aging assassin (Smith) facing off against his own clone 25 years his junior, at the peak of his abilities.

The film is being release Oct. 4, 2019 by Paramount Pictures, which partnered with production company Skydance Media for the film.

Jerry Bruckheimer, David Ellison, Dana Goldberg and Don Granger are producing the film, with Don Murphy and Chad Oman serving as executive producers. The project’s storied development history includes a script for the film that first surfaced in 1997, when the project was set up at Disney as a pitch by Darren Lemke, with Murphy producing and Tony Scott directing.

However, the de-aging technology that Disney used at the time from its now defunct visual effects division The Secret Lab, wasn’t enough to get the film off the ground. Today, such CG work as been used to impressive effect in films like “The Curious Case of Benjamin Button,” “Rogue One: A Star Wars Story” and Marvel films such as “Captain America: Civil War” and “Ant-Man and The Wasp.”

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“One of the reasons the movie is finally being made is that the technology is at a place where it’s possible to make it and to make it well,” Winstead said. “The technology is really kind of experimental in a lot of ways. I think Ang is really pushing the boundaries of filmmaking and the visuals and the experience of watching a movie.

“It’s hard for me to describe because I’m not the most tech savvy, but I think you’re going to be experiencing a completely new way of watching a movie and I’m really really excited to see the final film,” she added.

The shoot was long, taking six months. Luckily, Smith was on set, and Winstead said she never saw him aggravated, annoyed or grumpy.

“He truly is just the most wonderful, wonderful person,” Winstead said. “He was just this shinning light. He’s just so lovely and warm and so respectful — just like thankful to be there, you know. You don’t really find that in people in his position… it was a really amazing thing to witness.”

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Winstead was also recently cast as The Huntress in Warner Bros. all-female superhero team-up “Birds of Prey.” Winstead will star in that film alongside Margot Robbie and Jurnee Smollett-Bell, and it’s being directed by Cathy Yan (“Dead Pigs”) from a script penned by Christina Hodson, who is also writing “Batgirl” for the studio.