LAS VEGAS-Some of Hollywood's biggest movie studios took center stage at the CinemaCon on Tuesday - wheeling out a vast array of stars to promote their upcoming slates of blockbusters.

Historic "major" Paramount competed with new kid on the block STX for the loudest applause at the annual Las Vegas gathering for the "exhibition community" of theater operators and audio and visual tech innovators.

And while Disney traditionally keeps back most of its juciest surprises for its own D23 Expo, the studio treated delegates to a world premiere of the latest "Pirates of the Caribbean" movie, "Dead Men Tell No Tales."

Hollywood decamps to the Nevada desert for four days every year, taking over the iconic Caesar's Palace hotel to show theater operators what they can expect to be making their money from over the following 12 to 24 months.

STX, in business for just two years, was first up, putting forward legendary sci-fi director Luc Besson to present footage from his latest adventure, "Valerian and the City of a Thousand Planets."

The 58-year-old French auteur has made a string of hits, including "The Fifth Element," "Leon: The Professional," "Lucy" and "Nikita."

But he said his upcoming movie has been a passion project since he began reading the serialized 1960s comics from Pierre Christin and Jean-Claude Mezieres on which it is based.

"There was no internet, no YouTube, nothing and you had to wait a week to get two more pages," he told delegates at CinemaCon.

"I got totally addicted... It was so cool at the time, really new and I never stopped thinking about it."

The $180 million "Valerian" - which comes out on July 21 - centers on a dark force threatening Alpha, a vast metropolis and home to species from a thousand planets.

Blacks ops agents Valerian (Dean DeHaan) and Laureline (Cara Delevingne) race to identify the marauding menace and safeguard the universe.

The audience was treated to a new trailer, a surreal but self-aware fever dream in vivid 3-D featuring a huge, drooling CGI dog-like monster that rips a bus apart, as well of plenty of large Zen-like aliens and desert vistas with echoes of Mad Max.

Numerous stars, including Jessica Chastain, Aaron Sorkin, Mark Wahlberg and Mila Kunis took to the stage to discuss upcoming projects in various stages of development.

Wahlberg introduced action flick "Mile 22" saying he hoped it would be "the thing that defines me," while Kunis chatted about motherhood and the sequel to smash-hit "Bad Moms," due for release in November.

Oscar nominee Chastain stars in "Molly's Game" as Molly Bloom, a real-life skier who lost out on her Olympic dream and became an organizer of underground poker games for the Hollywood elite.

"I like that the film explores female power and what that means in society," said Chastain, who got to meet Bloom during production.

It was a busy day for Wahlberg, who was among a role call of A-listers enlisted in Paramount's afternoon presentation at a packed Colisseum theatre.

The studio launched its two-hour extravaganza with Dwayne Johnson and Zac Efron fronting the segment for "Baywatch" - the upcoming big screen adaptation of the popular 1990s lifeguard show.

Surrounded by 20 scantily clad models in "Baywatch" beachwear, Johnson called up Efron, Jon Bass, Alexandria Daddario and Priyanka Chopra, and declared: "I give you the Avengers of the Beach, Team Baywatch."

George Clooney, Matt Damon and Julianne Moore took to the stage to present footage from "Suburbicon," providing the first genuinely comedic moment of the afternoon.

Clooney - who directed the noir thriller from a script by the Coen brothers - cheekily berated Paramount and Damon for its decision to release "Suburbicon" on November 3, the same day "Thor: Ragnarok" hits theaters.

"Who's Thor?" Clooney, 55, wanted to know.

"I'm Thor, if I don't use my thaddle. Theriously," replied Damon.

The 46-year-old was back onstage later with director Alexander Payne to introduce the first footage of "Downsizing," a comedic satire based on a world where people can be shrunk down to save on household bills.

Then Anthony Hopkins, Wahlberg and other cast members from "Transformers: The Last Knight" were sent on with director Michael Bay to discuss the technological advances which went into making the movie.

Disney's evening presentation offered little in the way of breaking news on its upcoming slate, which includes "Guardians of the Galaxy Vol. 2" and the hotly anticipated "Star Wars: The Last Jedi."

But attendees did learn the name of the long-awaited sequel to the smash hit animated feature "Wreck-It Ralph."

"Ralph Breaks the Internet: Wreck-It Ralph 2" hits theaters in 2018 with a returning voice cast led by John C. Reilly and Sarah Silverman.