In "Sin City: A Dame to Kill For," Jessica Alba took direction from comic-book legend Frank Miller via his sketch pad. (The Weinstein Company/AP)

They aren’t the words you expect to hear from a screenwriter. But when this author of hard-boiled crime-noir is pressed for details, he sings.

“I find that, if I may say so, a screenplay is a gawdawful form.”

The reporter pulls the phone closer. The screenwriter spills.

“It’s just a dreadful way to translate an idea for a movie into a movie.”

Frank Miller, the comic-book legend turned filmmaker, is building up to a secret. “For me, the key is to draw constantly [on set]. When I was drawing, to an actor, he or she would immediately understand what I meant.” And when one of the world’s most noted cartoonists is behind the camera, the production takes full advantage of his manifold artistic gifts.

With the official opening Friday, Miller brandishes his latest piece, “Sin City: A Dame to Kill For,” a gritty, highly stylized 3-D picture he shot with his simpatico co-director, Robert Rodriguez, nearly a decade after they first turned stories from Miller’s serialized “Sin City” comic epic into a surprise cinematic hit. Actors who love dark, stark, grown-up comics seem to love to work with Miller.

“Here’s one anecdote,” Miller the storyteller invites. Referring to one of his many returning “Sin City” actors, he say, “I had come up with a shot of Jessica Alba with her crossbow, and I drew it in my style. I tend to draw very extreme figures and impossible poses. I looked at the set, and [suddenly] there she was, in exactly the pose I drew. I said, ‘Jessica, how did you do that?’ ‘That’s what you drew,’ she said.”

Is Miller — the man who already has topped the weekend box office once this year with “300: Rise of an Empire” — just spinning a great tale?

No, says Alba, who was helped immensely by Miller’s ability to communicate through spontaneous on-set sketches.

“I could [work] from the expressions, just the way he would draw you while looking at you,” says Alba, who stars as an avenging exotic dancer. “He would just sketch on set when he was inspired.”

Before Miller would even finish drawing, Alba says she would re-create the position, figuring out how to find the right movement — even against a green screen, acting with objects that would be superimposed only later — and have it “read” as real.

“We would create it together,” Alba says.

The fedora-loving Miller knows this live-sketch collaboration is unusual, and he also understands why it works.

“Actors love all the information they can get,” Miller says with a warm, raspy voice. “They always ask me who they are, where they came from — all these things that have nothing to do with the actual performance per se. . . . I give them the drawings to show them exactly what I’ve got in mind.”

Nearly a quarter-century ago, of course, Miller first began sketching this chiaroscuro, black-and-white world of “Sin City,” which debuted in 1991’s “Dark Horse Presents Fifth Anniversary Special.” It’s a brutal universe of thugs and .45 slugs, of powerfully corrupt politicians and self-policing prostitutes — and even the occasional cocky card sharp with the too-sharp hand.

Miller was born 57 winters ago in Olney, Md., but his family soon moved to Vermont, a landscape that the author says may inform his flair for drawing swirling snow. But his real environmental influences for works such as “Sin City” have been Los Angeles and New York. (Miller now lives in the latter city’s Hell’s Kitchen neighborhood.)

He broke into big-time comics in the late-’70s and soon returned the Marvel superhero Daredevil to relevancy with an Eastwood-like swagger. In the 1980s, Miller made great stylistic leaps, reaching perhaps his superhero pinnacle with 1986’s “The Dark Knight Returns.” There, he set Batman on a grittier path, one that influenced such directors as Tim Burton and Christopher Nolan.

With Rodriguez, a Texas-based filmmaker, Miller got the chance to transition from the artist’s stool to the director’s chair.

“The first time I met him, in November of 2003, I showed him a test I had done for a ‘Sin City’ proposal, and we were soon laughing it up,” Rodriguez says by phone during a break from shooting his new El Rey network drama, “Matador.” Everything between them clicked creatively.

“We’re the same guy,” Miller tells me.

A bit later, Rodriguez says independently: “We’re the same guy.’ ”

“I grew up with three brothers,” Miller continues. “With Robert, I feel like I’ve got a fourth. . . . Because we work so closely together, we can’t always remember even who came up with what.”

It helps that Rodriguez (”El Mariachi,” “Machete,” “Spy Kids”) was a cartoonist before he became a director; he drew a strip called “Los Hooligans” in high school, and he deeply appreciates Miller’s visual aesthetic.

When they teamed on the first “Sin City,” Rodriguez insisted that Miller be his co-director, even, he says, quitting the Directors Guild of America when the union objected to their twin-director credit. “Being a cartoonist myself, I told Frank to come direct me,” Rodriguez says. “Actors are your paper characters. You use a pen instead of a camera. It’s the same creative process — you’re just using slightly different tools.”

Their approaches are so similar, they say, that the collaboration became symbiotic and seamless. “When we disagree, it’s always toward the same goal,” Miller says.

They shared a vision for the first “Sin City,” which featured the worn and distinctive faces of such actors as Mickey Rourke, Bruce Willis and Powers Boothe and the lithe movements of such actresses as Alba and Rosario Dawson, all of whom return for the sequel. New to this mostly leached-of-color universe are Josh Brolin and Joseph Gordon-Levitt, as well as Eva Green as the Barbara Stanwyck femme fatale — if Stanwyck were making green-screened, R-rated movies with wardrobe optional.

The “Sin City” films may put the “graphic” in “graphic novel” in ways once forbidden in film, but the language is vintage noir.

“You feel like every character he creates is a piece of him or a fantasy within him,” Alba says of Miller. “You can relate to these raw emotions [within] the heightened genre.”

And what about the preponderance of scantily clad women in this Miller vision? What should we see — if not see-through — in how the author is rendering his female characters?

“If anything, Frank’s scared of us,” Alba says with a laugh. “He puts women on such a pedestal. In the ‘Sin City’ universe, they’re the ones running the [world], not the guys.”

“They are playing powerful characters, and they certainly don’t mind playing sexy,” Miller says of his “Sin City” actresses. “I don’t dress them up in burlap sacks. The idea is for them to look their best and be their strongest.”

And if there’s any doubt how to achieve that look and strength, Miller is ready to illustrate the effect, ever with drawing pad on set. In a world of sketchy characters, no one sketches this world better.