With the exception of a ride on a cable car, the mutant heroes and villains in the big action movie "X-Men: The Last Stand," which opens Friday, pretty much complete the San Francisco tourist checklist.

Magneto, Wolverine, Angel and the rest walk across the Golden Gate Bridge, visit Alcatraz and camp out in Muir Woods; they wander to the Marin Headlands and Golden Gate Park, and even take time for a quick flyby over North Beach.

But although the movie takes place in the Bay Area — and San Francisco landmarks figure significantly in the plot — no actor set foot in the city and almost no live action film was shot here.

Unknown to most moviegoers, special-effects innovations have reached the point where a filmmaker can set a $100 million summer blockbuster in an exotic locale without sending the usual fleet of actors, makeup artists, cinematographers and key grips there.

It's a growing strategy by movie studios grappling with the nearly 8 percent drop in box-office receipts from 2004 and 2005. As the visual effects get better and costs for filming in beloved locations like Paris, New York and San Francisco remain high, studios are finding it significantly cheaper and faster to build sets on back lots and use models and computers to fill in scenic backgrounds.

While the third "X-Men" movie is an extreme example because so few crew members actually touched ground in San Francisco, every big action movie released this season has filmed at least one scene using similar techniques.

"The technology is evolving so much faster than any of us as observers are aware," said 20th Century Fox President Hutch Parker, who helped supervise the "X-Men" film and is executive producer of this summer's remake of "The Omen." "It has in some ways made the prohibitively expensive affordable. I'm not going to say we couldn't have done this five years ago, but it wouldn't have been as convincing."

Fooling moviegoers into thinking they're seeing another place goes back more than 50 years, when a matte painting that served as a background shot could be used to depict a foreign locale. "Casablanca," for example, was not filmed in Morocco, but on a Los Angeles set — with the exception of the airport scene, which was shot at Van Nuys Airport. "The Maltese Falcon" did some location work in the Bay Area, but it, too, was mostly shot in Los Angeles.

For years studios used paintings and rear-projection techniques to fake locations, before computerized special effects started to take over the process in the 1990s. The 1994 Arnold Schwarzenegger summer blockbuster "True Lies" filmed much of the Harrier jet action sequence on a Los Angeles rooftop while using computers to fill in the Miami backdrop.

But most productions still combine the special effects touch-ups with on-location shooting that includes cast members. It's possible that no movie has done so much to fabricate a real-life location as the latest "X-Men" film, which features mutant metal sculptor Magneto — played by Ian McKellen — ripping the northern end of the Golden Gate Bridge off its foundation and relocating it to Alcatraz.

Not that everything in that scene was done with computers. A portion of the bridge actually existed — in a parking lot in Vancouver.

John Bruno, visual effects supervisor of "X-Men," said the art department built a full-scale piece of the bridge in Canada, which was about the size of a basketball court, and used computers to fill in the rest of the bridge and background. With the exception of a few FasTrak diamonds, the finished product is hard to tell from the original. "We had the right reflectors on the road and the right stains on the road," Bruno said. "We had the right amount of dirt and dust on the raised walkway of the bridge."

The decision to build replicas of San Francisco landmarks in another country may be alarming for professionals in the local film industry, who along with Mayor Gavin Newsom have been aggressively trying to lure studios to San Francisco — which passed the state's first film and television incentives program in April, giving filmmakers who shoot in the city a break on city fees.

But such efforts may fail to lure producers on tight budgets and schedules. The crew of "Mission: Impossible III," for example, was sent to Shanghai for a few weeks, but spent months building and filming a fake Shanghai in Los Angeles.

"The producers were thinking this could get very expensive with a lot of crews waiting around for something to happen," said "Mission: Impossible III" visual effects supervisor Roger Guyett, who worked for Industrial Light & Magic, based in the Bay Area. "The reality of making big movies is, your daily nut is huge. The cost of location shooting is astronomical, because of the support crew that's required to travel. And the last thing you want to do is go somewhere and not be able to achieve what you want."

Guyett said among the problems with filming in Shanghai is that the city encourages its citizens to turn off their lights at 10 p.m. This would have given director J.J. Abrams a narrow window to shoot the vibrant backdrops he wanted. Fog, haze, safety issues and other considerations led the team to build a pseudo-Shanghai in Los Angeles — using computers to fill in whatever they couldn't construct.

Bruno, a Bay Area native from Pittsburg who worked for ILM in the 1980s and used to live in San Francisco, said the "X-Men: The Last Stand" team couldn't have filmed on the Golden Gate Bridge even if they wanted to.

"We couldn't film on the bridge. We couldn't get within a quarter-mile," said Bruno, who spent a week in the Bay Area in October getting the background photos they needed to make the special effects. "We basically walked on it and took still pictures. The other photographs we took of the bridge were done from a helicopter — right to the point where they waved us off."

Guyett suggests there's a real market for building fake bridges. "We actually built our version of the Chesapeake Bay Bridge just outside of L.A., in Calabasas," Guyett said. "We just built it on a piece of waste ground with a clear horizon on the top of a plateau out there. When you see the water, it's all just made up."

Some of the same tricks used in "X-Men: The Last Stand" and "Mission: Impossible III" are being worked into relatively low-tech films. Location scout Scott Trimble remembers photographic plate shots being taken for "Dr. Doolittle II," a movie that filmed in the Bay Area but used special effects to enhance backgrounds such as Lucas Valley and Mount Tamalpais.

Trimble said the practice is even more widespread on television, where shows such as "Charmed" and the "The Chris Isaak Show" and the recent "The Evidence" are based in San Francisco and film mostly or entirely in Vancouver or Toronto.

"There's definitely been more of it," Trimble said. "On TV, a great example of this is 'Alias.' The show is set in just about every country all over the world, but it's shot entirely in Los Angeles. They can add the Eiffel Tower over some building rooftop."

They can even substitute an entire forest, although Muir Woods in the new "X-Men" movie wasn't done with special effects. Producers borrowed a forest near Vancouver, and also subbed in a park setting at Pinewood Studios in England to replace Golden Gate Park.

Sunday roller-bladers and regulars at the M.H. de Young Memorial Museum may be able to tell the difference, but it's likely few outside of San Francisco will. And even if they can, the studios will probably just find another way to simulate the park — short of actually going there.

©2006 San Francisco Chronicle