LOS ANGELES, July 26 ― Will Smith does battle with a younger clone of himself in new sci-fi action thriller Gemini Man, which filmmakers say represents Hollywood's biggest leap forward yet into futuristic computer generated imagery.

Several movies have employed "de-aging” techniques to airbrush away wrinkles on grizzled stars, but the fresh-faced younger Smith in Paramount's film is entirely built with special effects ― right down to his eerily realistic pores, sinews and blood vessels.

"In the past we would have had Will Smith's son play it ― he would have been put in different hair and makeup, and we'd have called him a 'clone',” director Ang Lee told reporters in Los Angeles.

"But it doesn't look good in this media,” he added, referring to the film's state-of-the-art 3D shots, which include several close-up, visceral fight scenes.

Gemini Man has been trapped in development for more than two decades, bouncing between studios, directors and stars as Hollywood has waited for technology to catch up with the movie's plot ― the trailer shows a young clone assassin sent by a shadowy organization to kill his older self.

The techniques used in the upcoming film, out in October, are similar to those used in Disney's recent "live action” version of The Lion King.

But creating a realistic-looking human face has been an unachievable goal of visual effects for a long time, said effects supervisor Bill Westenhofer.

"Every single one of us are experts... over millions of years, the face is how we look at someone and tell that they're lying to you or that there's an illness,” he explained.

"The subtleties of what tells you that are subconscious. So for us to go in and try to recreate that digitally is really hard.”

Smith and stunt doubles acted out the younger character's part in motion-capture suits before the visual effects were applied on top of their movements.

Filmmakers went through old photographs and footage of Smith from his twenties ― the age of his character's clone "Junior” in the film ― including Bad Boys and Independence Day.

They studied the morphology of aging, and looked at human anatomy from how facial muscles interact right down to the microscopic level of skin pores and melanin pigment.

Producer Jerry Bruckheimer, who has been on board with the project for over a decade, said the "revolutionary” leap in technology and detail was the equivalent of "going from black and white into colour.” ― AFP-Relaxnews