Much has been made of New Line founder Bob Shaye’s gutsy decision to bankroll the “Lord of the Rings” trilogy, but what hasn’t gotten enough attention is how much Peter Jackson helped his own cause by paying $50,000 to make a 30-minute short film.

It was a short that, by all accounts, was the deciding factor in his getting a greenlight from Shaye on what is now on course to become one of the most profitable film franchises ever.

Dish viewed the film, which until now had been seen only by Jackson, his reps, Shaye and Fine Line president Mark Ordesky. The short was a last-ditch effort to rescue “Rings” from the Miramax turnaround scrap heap and was enough to persuade Shaye to finance three films instead of the two Jackson asked for.

It also showed convincingly why Jackson was the right director for the “Rings” job even though he was coming off the failure “The Frighteners.”

After long developing “Rings” only to fail in securing a partner to make two films, Miramax gave Jackson back the film under prohibitive terms. He had three weeks to hook another studio, which would have to repay the $12 million spent by Miramax, and give up 5 percent of first-dollar gross.

Unbowed by those arduous terms, Jackson retreated to New Zealand bent on making promotional film that would show that the ambitious “Rings” movie was possible because of the $12 million that had been spent on rights, special effects and visuals to bring Middle Earth to life.

Narrating the short himself, Jackson introduced the artwork, models and computer imagery that would convincingly shrink actors to Hobbit size, make the Orcs grotesque by enlarging their eyes and make Herculean Uruk-Hai warriors believable through computer animation.

Jackson showed the armor, the architecture of the mines of Moria and the maniacal faces on the horses that would carry the black riders who pursue Frodo Baggins throughout the trilogy.

The film then featured storyboards coupled by dialogue read by unseen actors. What is most striking is how closely Jackson’s movie stuck to his initial game plan.

“So here we are,” he said at the close of the filmed pitch, “45 years after the publication of this book where finally the technology has caught up to the incredible imagination that (J.R.R.) Tolkien injected into this story of his. This movie can be made.”

In terms of salesmanship effort, Jackson’s film is reminiscent of the short made by Robert Evans three decades ago, the one that persuaded Gulf & Western not to fold Paramount Pictures and sell the backlot.

Evans, who headed production at the time, got Mike Nichols to direct him in an appeal that promised upcoming projects like “Love Story” and “The Godfather” would right the studio’s course.

“The lot was set to become part of this Jewish cemetery right behind it, and you don’t see any dead bodies there now, only a lot of soundstages,” Evans said. “I didn’t get a bonus or anything, but I walked out of that meeting with the autonomy needed to make Paramount a power.”

Viewings of Evans’ film have been limited to visitors in his private screening room, but Evans said the footage will be in the Graydon Carter-produced documentary “The Kid Stays in the Picture.”

As for Jackson’s half-hour film, New Line hasn’t yet decided whether fans will get to see it. It would be a worthwhile addition to the DVD, at the least.