By then, Sina had founded a nonprofit called intimacy Directors International with two other women-Siobhan Richardson, a movement coach, and Rodis, who had been doing some informal intimacy coördination for a stunt program at N.Y.U.’s film school. I.D.I. had a “janky website,” as Sina put it, but it was enough to get noticed by HBO.

After the L.A. Times published its story about Franco, David Simon, a creator of “The Deuce,” released a statement clarifying that there had been no complaints on set against the actor, who had also directed several episodes.Privately, the show’s lead actress, Emily Meade, threatened to quit.She didn’t want to be implicated in a message that she felt downplayed the allegations, she told me. The network asked what it could do to persuade her to stay. Meade had never heard of an intimacy coördinator, but she requested “an objective party to make sure everybody’s O.K.” during the sex scenes. Reflecting on it now, she can’t believe the network said yes. “It was a sliding-doors moment that I don’t think would have happened at any other time and place,” she told me.

Rodis met with each actor individually and then took their concerns to the director, as is now common practice. She also helped with “silly aspects,” Meade said, like bringing the actress kneepads for a blow-job scene.

That October, when HBO announced it would staff every production with an intimacy coördinator, the network had to get creative-colleges were not exactly graduating intimacy majors. Amanda Blumenthal, who had just completed a course at Somatica, an institute in Berkeley, California, that trains sex-and-relationship coaches, was hired after her mother, an HBO executive, mentioned that the network was looking for “this thing called an intimacy coördinator” on a new show, “Euphoria.” Mam Smith,a former stunt performer,was brought in to work on the third season of “Westworld.” Smith told me, “On my first day, there were two hundred naked extras, all painted blue, and they had to be wet, because the story was that their characters had been in cold storage.” Smith made sure that there were warming tents and requested additional wardrobe crew to hand out robes.

By 2019,intimacy coördinators were even working with actors playing intimacy coördinators. In “High Maintenance,” an anthology series that aired on HBO, about New Yorkers who have the same weed guy, a character named Kym (Abigail bengson) choreographs two actors (Nick Kroll and Rebecca Hall) portraying a campaign manager and a politician having sex in a field office. “How do we want to get to this desk?” Kym asks them. On HBO’s “The Idol,” Lily-Rose Depp, playing a troubled pop star, is so annoyed by the intimacy coördinator trying to enforce a nudity rider for a photo shoot that her team locks him in a closet.

Things were moving quickly, perhaps too quickly. “There was a fear that this whole thing was going to get scrapped if we let the wrong person in,” Rodis told me. One aspiring intimacy coördinator suggested that productions set aside spare rooms for people to masturbate in after sex scenes. “I was, like, ‘Oh, no, no, no. We’re at work,’ ” Rodis said.

In 2019, the actress Gabrielle Carteris, then the president of SAG–AFTRAgot nervous that the splashy headlines about sex choreographers for movie stars were going to attract the other kind of bad actor.She and the union’s executive director, David White, convened a series of meetings with more than a dozen intimacy coördinators-Rodis, Blumenthal, and Duenyas among them-to draft a list of official protocols for the position, such as safeguarding “closed sets” and reviewing final cuts to check compliance with nudity riders. Carteris also established a registry to aid producers in identifying qualified candidates, whom the union defined as someone who had spent sixty days on a SAG–AFTRA set as an intimacy coördinator. “We wanted to create a standard that could be upheld,” she told me.”I didn’t want it to be where anybody could do this.”

But others saw the registry as gatekeeping, and some feared that producers would prefer intimacy coördinators who had undergone a pricey SAG-approved training program (rather than learning on smaller jobs or student films).Chelsea Pace, an intimacy coördinator and a former movement professor at the University of Maryland, Baltimore County, worried that the competition to get onto hollywood sets would lead to a certification gold rush. “There were a lot of people, like myself, who had years of experience choreographing intimacy and now had to spend thousands of dollars to get a star on their folder having mentioned that, ‘Hey, you’re eligible to do this now,’ ” Pace said.

Professionalization also changed the tenor of the job. In 2015, Duenyas had worked on the Thomas Bradshaw play “Fulfillment”-about a lawyer sleeping with a co-worker-as a sex choreographer. “It felt really fun to call it that, because there’s so much shame around sex,” Duenyas said to me, sounding nostalgic.

In 1980, the director Francis Ford Coppola hired Constance Penley, a berkeley Ph.D. candidate and an editor of a feminist film journal, as a research assistant on “One from the Heart,” a Vegas-set musical romance. The script included a sex scene, and Coppola asked Penley to identify what the best ones had in common. Coppola,Penley told me,”gave me an office at Zoetrope and a telex that I could use to call whomever I wanted and say,’Francis wants to no,What is the most erotic scene in film?’ ” Susan Sontag said that for her it was the wind blowing through Barbara Stanwyck’s hair at the end of “The Bitter Tea of General Yen.”

After reviewing hundreds of films, Penley gave Coppola a report that outlined two main criteria for a good erotic scene. First, the characters are not supposed to have sex. “There has to be some big difference between the two,” she said, one that makes their encounter unlikely.second, one or both of the characters is “under threat of death.” As an example, Penley offered the sex scene between Linda Hamilton and Michael Biehn in “The Terminator,” in which the latter plays a man from 2029 who has travelled back in time to rescue Hamilton’s character from a cyborg assassin played by arnold Schwarzenegger. “If you see it out of context, it’s O.K.,” she said. “But when you know he’s from the future and they’re being hunted, it’s really, really hot.”

My favorite sex scene, I realized, fit the formula. In “out of Sight,” Jennifer Lopez, as Detective Karen Sisco, finally comes face to face, at a hotel bar, with George Clooney’s Jack Foley, a handsome bank robber she has been trailing.There’s an implausible pairing and the likelihood of a shoot-out dénouement, and so when Sisco tells him, “you really wear that suit,” it’s obvious that it will soon be coming off.

Penley’s formula also helped me see why certain scenes without a hint of sex still felt suffused with erotic energy. In Claire Denis’s “stars at Noon,” margaret Qualley plays a righteous American journalist in Nicaragua who falls for a naïve British oil executive (Joe Alwyn) unwittingly in the way of an American plot to control the industry.Their lovers-on-the-lam sex scenes did nothing for me. Yet when Qualley’s character, thinking she’s finally lost the couple’s tail, walks into a dilapidated restaurant and spies Benny Safdie in a C.I.A.-issued Hawaiian shirt, and he asks, “Do you mind sitting down and watching me eat my breakfast?,” I was rapt. I called Denis in Paris,and she seemed to confirm Penley’s hypothesis. “They are both defending something, but they’re on the opposite side,” she said.Plus, she added, “There’s something so sexy about saying, ‘You’re with the wrong guy.’ “

But intimacy coördinators believe that, even after a script’s narrative has been steadfast, they can augment erotic tension through sex choreography, which I learned has a vocabulary all its own. On a dry-erase board, Duenyas had written a glossary of technical terms from Chelsea Pace’s textbook, “Staging Sex: Best Practices, Tools, and Techniques for Theatrical Intimacy.” The first word was “distance.” (An intimacy coördinator would not say “make out” but, rather, “close the distance between your mouths.”) Another term was “shapes.” (Instead of telling an actor to “grind on” his co-star, one might say, “make a figure eight with your hips.”) Shapes, Duenyas told us, “are when you can really start telling stories.”