At a certain point in the past decade -- after the Jennifer Lopez movie and before the Jennifer Garner one, sometime between the two with Kate Hudson -- Matthew McConaughey became a genre unto himself. For a while, it seemed, the makers of American romantic comedies were in the grips of repetition compulsion. Not only did many of these movies ("The Wedding Planner," "Ghosts of Girlfriends Past," "Failure to Launch") have barely distinguishable posters and plots, McConaughey also served a constant function in them: Usually playing an upwardly mobile urban professional, he was a tanned emblem of a fantasy of modern masculinity, roguish but secretly sensitive, indecisive but (when push came to shove) true. His eye-crinkling grins and caddish smirks were not just the films' principal weapons; often they were their very reasons for being.

By way of contrast, consider a few of McConaughey's roles from this year alone. In Steven Soderbergh's "Magic Mike," he struts away with the movie as an aging beefcake dancer turned sleazy emcee-owner of a Tampa strip club. In William Friedkin's Texas noir "Killer Joe," due Friday, he has the title role of a sociopathic, Stetson-wearing cop and part-time hit man with a baroquely sadistic streak and a dead-eye stare behind his aviator shades. In Lee Daniels' sweaty Southern Gothic melodrama "The Paperboy," the talk of the Cannes Film Festival in May, he goes even further against the grain, playing a closeted gay reporter

Reunited

And that's not all. In the recent true-crime tale "Bernie," McConaughey burnished his character-actor credentials as a larger-than-life small-town prosecutor -- and reunited with the director Richard Linklater, who gave him his big break two decades ago in "Dazed and Confused" (1993). McConaughey also proved his ability quietly to anchor a modest, old-fashioned movie, as a fugitive who befriends two Mississippi boys in "Mud," a Huck Finnish slice of Americana from Jeff Nichols ("Take Shelter"), which also had its premiere at Cannes. Suffice it to say these are all characters defined by rather more varied and interesting predicaments than an inability to commit. For an actor whose filmography had come to resemble one interminable in-flight movie, this unfolding chapter -- even if it means "humongous pay cuts," in his words -- counts as a major reinvention.

Keeping prepared

The difference between then and now is so pronounced that McConaughey acknowledged he had been hard-pressed to explain what happened. When a reporter approached him at the Greenwich Hotel in Tribeca recently, he was lost in thought, scribbling on a notepad. Everyone who spoke about McConaughey for this article remarked on his penchant for preparation, and it turns out he was taking notes for the interview. "I've gone back and looked at some of my diaries to try and see, where was my head at?" he said.

As he tells it, there was no epiphany. "I didn't just say, hey, line in the sand, I'm done with that, let's begin with this," he said. But there was a point a few years ago when he realized that the scripts coming his way, mostly romantic comedies and a few action adventures, were invariably "kind of boring." The same offers kept rolling in -- and no wonder, for most of McConaughey's romcoms each took in more than $100 million worldwide -- and he kept saying no.

It wasn't long before Hollywood got the message. "In a wild, cyclical way I started to attract these other things," McConaughey said. The turning point was last year's well-received thriller "The Lincoln Lawyer," his first film after a two-year absence from movie screens. The part of a glib, swaggering lawyer was not a huge stretch, but he attacked it with relish, and it must have signaled a readiness for new challenges. In quick succession the directors -- veterans and indie up-and-comers alike -- came calling.

A midcareer swerve like McConaughey's is hardly unprecedented: Tom Cruise mixed things up with left-field parts in "Magnolia" and "Tropic Thunder" (which also featured McConaughey), and John Travolta famously rebooted with "Pulp Fiction." But few have pulled off so complete and sustained an overhaul.

"I'm having a lot of fun," McConaughey said, noting that it has been a big year by any measure: He has five movies coming out, walked the Cannes red carpet twice in May and married his longtime girlfriend, Camila Alves, last month. (They have two children and recently announced that they are expecting their third.) In conversation, McConaughey was expansive and affable, even "mannerly," a word he used several times. Generous with eye contact and back pats, he spoke in winding monologues and colorful analogies and was especially animated on the subject of his newfound freedom as an actor.

"There are zero shackles," he said, noting what his recent characters have in common. "They definitely make up their own rules." Much like Paul Newman's antihero in "Hud," a favorite of his, these are men who "walk in a straight line all the way to the end of the picture -- no placation, no pandering," he said.

McConaughey, 42, takes evident delight in tarnishing his golden-boy halo. "The hero, the white knight -- he's usually on the right side of morality," he said. "But these guys I've been playing are more amoral." There is no clearer example of this than the perverse "Killer Joe," based on an early work by the Pulitzer Prize-winning playwright Tracy Letts. McConaughey admitted he was put off on a first read, but a discussion with Friedkin helped him see the pitch-black humor.

A knack for macabre

The new, improved McConaughey does not exactly come out of nowhere. He showed a knack for macabre material in Bill Paxton's psychological drama "Frailty" (2001), which Friedkin said convinced him that this actor was right for "Killer Joe." And McConaughey's first significant role -- as a skirt-chasing slacker in "Dazed and Confused" -- remains the best encapsulation of everything distinctive about him: his lothario charm and showboat flair, the lazy drawl and sneaky dead-on timing, the sly capacity for both self-infatuation and self-parody.

Most of those qualities are on view in "Magic Mike," in which McConaughey plays the utterly absurd Dallas with an impressively straight face. "He's this poet-capitalist-warlord-messiah of the male revue world," McConaughey said. "None of that's funny until you say 'of the male revue world.' " For a scene at a gym he encouraged the wardrobe department to pile on the indignities: he ended up in a cutoff T-shirt, skintight shorts and ballet shoes, a look he described as "Baryshnikov meets Richard Simmons."

Careful role selection

On "The Paperboy," Daniels, who likes to cast against type, said he tried to "make Matthew as physically unattractive as I could, which is kind of hard." He added: "And I would tell him, no talky talky, just show me your eyes." For at least one viewer it was a successful attempt to efface all traces of the movie star. "My mother was very disturbed," Daniels said. "She loves Matthew McConaughey, and she said, 'What have you done to my Matthew McConaughey?' "

Friedkin said careful role selection is all the more important for someone of McConaughey's looks and stature. "I know how little they value the acting of a great-looking guy in Hollywood," Friedkin said. "They don't want you to act, they just want you to show up and convincingly make love to the leading lady. A guy like Matthew has to take charge of his own career, because the studios will cast him in the same part every time out."

McConaughey is aware there is a perception he was coasting in those romcoms; he maintains it was harder work than people think. "I've done romantic comedies that were more difficult than 'Killer Joe,' " he said. "The work is to keep them buoyant. If you dig deep, you try to go to the reality and to the humanity, it's a 12-minute movie."

McConaughey said he was determined to keep his films interesting, though that doesn't mean indies only. He next stars with Woody Harrelson in "True Detective," a new HBO series, and has what sounds like an award-baiting lead in "The Dallas Buyers' Club," based on the true story of an HIV-positive man in the 1980s who turned to underground pharmacies.

McConaughey looked down at his notes and picked out something from a diary entry a few years ago: "I found this bit where I was saying: Hey, let's not go do one for me, one for them. Let's go do one for me, two for me, three for me, four for me, five for me, and hope like hell it could be one for them."