Now that the franchise has replaced the blockbuster as Hollywood’s holy grail, a new tool has emerged to help those who want to extend film and TV properties across multiple platforms.

The tool — transmedia storytelling — is capable of performing such feats as the recent revival of the Batman franchise, which helped propel “The Dark Knight” to the second-highest box office numbers in history, after “Titanic.”

“They resurrected a dusty old brand that ran into trouble in the early ’90s,” says Jeff Gomez, co-founder of Starlight Runner Entertainment, which specializes in applying the transmedia approach to studio tentpoles. “The filmmakers were able to go back to the essentials — the true, deep conflict that the character faces — and they managed to make it resonant with our current conflicts as a society.”

Transmedia takes the concept of the bible — a document containing backstory information that film and TV writers rely on for building plots and characters — to an extensive new level.

The idea of developing a piece of intellectual property in a consistent manner across multiple media platforms was pioneered in its modern form by George Lucas, who turned his first “Star Wars” film into five more features, multiple TV shows, a panoply of books and an onslaught of toys and games. The feature films alone have generated a cumulative worldwide box office of more than $4 billion.

What Lucas did went several steps beyond old-style character licensing and brand extensions. He created a unified body of work with an extensive backstory and mythology, and he determinedly guarded its canon while simultaneously opening up peripheral parts of his universe to exploration by other contributors.

And today, as the industry struggles to maximize auds and revenues, many producers consider transmedia a key to extending franchises across the additional platforms that have emerged in the three decades since the first “Star Wars” film.

“I grew up on ‘Star Wars’ and experimented with that stuff on my shows. It helped build a loyal fan base, connect with them beyond primetime and reach them in other parts of their lives,” says Jesse Alexander, co-exec producer on “Lost” and “Heroes,” and exec producer on NBC’s 2010-debuting skein “Day One.”

For “Day One,” an hourlong drama set in the aftermath of an unspecified event that destroys the global infrastructure, Alexander says he’s working with NBC Universal to develop ancillaries like a comicbook, a prequel novel and online content to be available on or before the show’s debut. “It helps to build out the franchise at launch,” he says.

“People are realizing that this kind of concerted implementation is one of the most powerful ways to convey messages,” says Gomez, who worked with Disney on “Pirates of the Caribbean” and “Tron,” and with Fox on James Cameron’s “Avatar.” “For them, as for most of our clients, we make sure the universe of the film maintains its integrity as it’s expanded and implemented across multiple platforms.”

Starlight Runner typically got involved with projects toward the end of their development, but more recently has been jumping aboard at an earlier stage, Gomez says. And producers are building the costs of creating a transmedia plan into the production budget rather than leaving it as an afterthought paid for by the marketing division.

“We’re now working with writers, producers and directors who are devising these worlds from scratch, rather than with the marketing people figuring out what to do with something that’s already completed,” he says.

Starlight Runner was founded in 2000 and has built a client list that includes Acclaim Entertainment, Coca-Cola, Microsoft, Showtime and Hasbro.

The company’s work “goes beyond your typical bible,” Gomez says. Starlight Runner creates “megabibles and mythologies” contained in oversized binders full of images, chronologies, storylines, character profiles and descriptions of such details as geography, vehicles and weapons. “We teach the studio, other divisions of its parent company and its licensors how to bring these characters to life in a way that’s true to the original platform.”

For example, Starlight’s mythology document for “Avatar” facilitated the extension of that property to the vidgame arena via publisher Ubisoft, which plans to release an Avatar game that, like the movie, will be available in stereoscopic 3-D.

Starlight began its relationship with “Avatar” via an introduction made by a senior studio exec with considerable franchise familiarity just as production on the film was getting under way.

“We always try to extend a property to other experiences,” says the exec. To do that, he adds, it’s important to “look at what the essence of the property is, what people are responding to, and re-create that in other ways.”

Another believer in the transmedia concept, scribe Danny Bilson, who’s steering production and marketing at vidgame publisher THQ, takes as his mantra the old Microsoft advertising slogan “Where do you want to go today?” “That’s different from ‘What do you want to watch?’ ” he notes.

Bilson’s main mission is to create successful games, but he’s always on the lookout for extensions that can be supported by the original vision. “Once I have the concept, I’ll talk to the movie guys about it,” he says. “Even before that, we’ll be looking to books for inspiration, or even to revitalize a movie that’s a dormant classic.”

Action figures and online components are launched at the time of the game’s release.

One Hollywood talent agent who works in new media says his clients “who own a piece of intellectual property that will be replicated on different platforms need to be intimately involved in extending that mythology” in order to preserve the property’s integrity.

“They can’t just let anybody do it,” he says. “It may not be just fanboys who are going to see a film like ‘Spider-Man,’ but those fanboys become your evangelists if you pay close attention to the mythology and make sure it sticks to the original thrust of the story. If you don’t, you can have problems.”

Another danger, says the agent, is that success can blind a property owner in a way that leads to missed opportunities.

“Once a property becomes big, you might not even realize you’re making a mistake. Your film is successful, but could you be doing more? Could you have extended it onto more platforms had you adhered more closely to the mythology? Probably so.”

Examples of franchises that have been hurt by the lack of an adequate mythology, or enforcement of a mythology, are legion, Gomez says. He singles out “The Crow,” the comicbook series that became a Brandon Lee starrer helmed by Alex Proyas.

“Efforts were made to extend that franchise, and the fanbase was game,” Gomez says. “But the sequels that came out either ignored or contradicted the set of rules established in the first film.”

To some degree, per Gomez, similar problems afflicted portions of the Terminator and Batman franchises.

With Terminator, there were issues as to who owns which rights to various versions of the property. “Without a central clearing house for the intellectual property, you had different groups pursuing different visions,” Gomez continues. “In the TV series and the new film, a number of core elements that people truly connected with were missing, resulting in products that didn’t maximize the brand’s potential.”

Says Alexander: “Revenue generation is a goal of all these initiatives. Beyond exposing the property to an audience, I try to find ways to build value for it.

“We’re all challenged to find new ways to make money,” he adds. “A cross-platform approach to narrative exploitation is a great opportunity for those who know how to do it right.”