The other self-funded American epic with a years-long production debuted at Cannes yesterday

Kevin Costner is big on believing, whether that’s in aliens or in himself. “I’m so grateful that I’ve never seen a UFO,” the actor-director said in a recent GQ cover story. “I’m a pretty sane person, although some people would think maybe something else. But what happens once you see one? You can’t let it go.”

That same staunch faith and inability to move on are the qualities that drove Costner to create Horizon: An American Saga, a planned four-part Western that he largely funded out of his own pocket. (“I know they say I’ve got $20 million of my own money in this movie… It’s not true,” he said. “I’ve got now about $38 million in the film… That’s the real number.”) Over the course of the saga’s production—which began long enough ago for him to name his now 15-year-old son after one of its characters—Costner faced a contentious divorce, controversy on the set of Yellowstone, and Hollywood’s doubts.

Still, he pressed on. Citing a conversation with his psychiatrist where she questioned why, he said, “I guess the answer is: Because I believe. But I can also see that psychiatrist going, ‘Yeah, but no one wanted one, and you just did four’… I can’t defend that psyche. I can’t defend anything other than the story just kept getting better and better for me.”

Now, part one of that story is officially out in the world. The three-hour film—which Costner wrote and stars in, in addition to directing—premiered at Cannes Sunday to a nearly 10-minute standing ovation. “I’m sorry you had to clap so long for me to speak,” Costner said as the applause died down (via The Hollywood Reporter). “It’s not mine anymore. It’s yours. I knew that the minute this was over. And that’s the way it should be.”

Like Francis Ford Coppola’s Megalopolis, this year’s other weighty, self-funded autuer epic, Horizon: An American Saga—Chapter 1 is currently pulling in mixed reactions from critics. The Hollywood Reporter called it a “clumsy slog” while Deadline lauded it as “an impressive beginning, with the promise of more to come.” Either way, the “more to come” part is undeniable. Chapter 1 opens for the rest of the world on June 28 with Chapter 2—which Costner’s already shot—following in close succession in August. “It’s never been done,” Costner told GQ of his plan to premiere two major projects in the same summer. “But I’m a little unconventional. I liked all four of ’em. They’re already written. I’m not making shit up on the fly. And so to me, it’s not over until it’s over. So I did them both.”

Even if his big gambit doesn’t work out, Costner is optimistic. “I think movies aren’t about their opening weekends, they are about their lives. And about how many times you are willing to share it,” he said at the film’s premiere. “I hope you do share this movie with your sweethearts, with your children.”