Joaquin Phoenix, whose star turn in “Joker” is already generating awards buzz, said he “wanted the freedom to create something that wasn’t identifiable” and did not let himself be influenced by any previous versions of the character or pin him down as a familiar type.

“What was so attractive about this character for me is he’s so hard to define. You don’t really want to define him,” Phoenix said Saturday at the film’s press conference at the Venice Film Festival. “Every day felt like we were discovering new aspects of his character…up until the very last day.”

Phoenix plays Arthur Fleck, a struggling comedian whose professional and personal failures finally push him to become the nihilistic, frightening Joker. To prepare for the role, Phoenix said he read a book on political assassins to get a sense of such killers and their motivations. But ultimately, that was for information only.

“I did identify Arthur as a particular personality, a particular type,” Phoenix said. But “I also wanted the freedom to create something that wasn’t identifiable. This is a fictional character. I didn’t want a psychiatrist to be able to identify the kind of person he was….Let’s step away from that, and we want to have the room to create what we want.”

Phoenix said previous essays of the role – such as Heath Ledger’s Oscar-winning turn a decade ago – did not influence him. “I didn’t refer to any past iteration of the character,” he said. “It just felt like something that was our creation in some ways.”

Besides Phoenix, “Joker’s” cast includes Robert De Niro, Zazie Beetz and Marc Maron. The film is directed by Todd Phillips and co-written by Phillips and Scott Silver.

With its dark and forbidding tone, the film differs from most comic-book movies. Phillips said he wanted to do something similar to the character studies seen in films from the 1970s, around the era in which “Joker” is set.

“Why can’t you do a genre comic-book film like that?” Phillips said. “We thought this could be an exciting approach to this genre. I’m not sure what it means for DC or Marvel….It was a hard movie for us to get made, to convince DC and the studio at first, but we thought we would keep pushing because we thought it would be special.”

The approach meant that they could try to create something totally new. “It was really liberating,” Phillips said. “There really were no rules or boundaries for it.”

Phillips said “The Man Who Laughs,” the 1928 film adaptation of Victor Hugo’s classic novel, was a “big inspiration” for him and Silver when they started developing “Joker.” Besides “The Man Who Laughs,” Phillips said he also drew inspiration from films by Martin Scorsese, notably “Taxi Driver,” “Raging Bull” and “The King of Comedy,” and Milos Forman’s “One Flew Over the Cuckoo’s Nest.”

Before its world premiere Saturday night, “Joker” had already enjoyed two packed press screenings.

The Warner Bros. film was arguably the most anticipated title in Venice’s official lineup when it was unveiled in July. The buildup and buzz on the Lido has been mounting since the festival began Wednesday, with festival chief Alberto Barbera declaring already that the film is “going straight to the Oscars, even though it’s gritty, dark, violent. It has amazing ambition and scope.”

“Joker” is standalone film set outside the usual DC Comics live-action universe. Although Ledger’s turn as the laughing villain in “The Dark Knight” won him the best supporting actor Oscar in 2009, that film did not delve so deeply into his back story. In a trailer released earlier this week, Phoenix’s Fleck can be seen gradually adopting his harrowing Joker persona until it takes over his identity completely.

“Joker” will also screen at the Toronto Film Festival. It is scheduled for release in the U.S. on Oct. 4.

Elsa Keslassy contributed to this report.