What happens when someone who is usually in front of the movie camera feels a calling to control what's behind it? Call them "personal projects" or "passion projects," they're films that successful actors struggle and sweat to get made just because, well, they want to -- because they have a story to tell, one that has more to do with the heart than the wallet.

Take Paul Reiser, perhaps best known for TV's "Mad About You" and the 1983 film "Diner." About 20 years ago, Reiser noticed his father laughing while watching Peter Falk in the movie "The Cheap Detective" on television.

The result: Reiser's recent movie, "The Thing About My Folks."

"I didn't have a need to make my own movie as much as I had a need to make this movie," says Reiser, who wrote the comedy and stars as a middle-aged man trying to heal family misunderstandings while on a road trip with his father, played by Falk.

Reiser was not alone in his desire to create a personally felt movie, however long and convoluted the journey from concept to screen.

Emilio Estevez has been working for 41/2 years to bring to fruition his independently produced passion project "Bobby," about events surrounding the assassination of Robert F. Kennedy. Casting was underway more than three years ago, but then the funding fell apart. Now he has again found financial backing, so cameras will start rolling in Los Angeles a week from tomorrow.

Patrick Swayze and his wife, Lisa Niemi, adapted their dance-themed play, "Without a Word," performed to critical acclaim in Los Angeles 18 years ago, into the movie "One Last Dance." It's just released on DVD. Rick Schroder began writing his film "Black Cloud," a boxing drama set in the Native American community in 2002, after his stint on "NYPD Blue." He also directed and played a role in the film, now on DVD after limited theatrical release. John Malkovich, with his production company Mr. Mudd, has been working for 10 years to bring the play "The Libertine," which Malkovich acted in, to the screen.

Then there's Peter Riegert, who has spent almost five years shepherding "King of the Corner" to the screen. He co-wrote the screenplay, directed and stars in this wry tale adapted from Gerald Shapiro's book "Bad Jews and Other Stories." Popular with critics, it's in limited theatrical release.

These filmmakers may be actors with longtime careers and considerable name recognition, but that's not much help within the blockbuster mentality that dominates the film industry, where even stars with high wattage have had difficultly getting pet projects made. Clint Eastwood had trouble persuading a major studio to chip in for production costs for "Million Dollar Baby," which eventually won the Oscar for Best Picture, and after major distributors shunned "The Passion of the Christ," Mel Gibson had to launch a grassroots release campaign, which ultimately earned him millions.

So how did these just-regular thespians pull off making their movies?

"I think if I felt less passionately about it, it never would have happened," says Reiser. "It had every reason not to happen. It was tough to raise the money. It was tough to get it sold. It was tough to do everything. I just literally refused to take 'no,' " says Reiser.

"Paul does say when he finished the script he brought it to the studios and every studio without fail said no. They all said no. He said even people without studios would call to say no," Falk says, chuckling. He said yes immediately after reading only 40 pages of the script Reiser had taken about two decades to complete.

This type of determination in the face of rejection reminds Falk of his friend the late director John Cassavetes, for whom he worked on 1970s films such as "Husbands" and "A Woman Under the Influence." "John could never get anybody to put up any money for his pictures either," says the veteran star, famous for his TV role as Lt. Columbo.

Lemore Syvan, founder of Elevation Filmworks, the independent production and distribution company behind Riegert's "King of the Corner," says Riegert likes to quote something the late actor-turned-producer Burt Lancaster used to say: "I make one for me, one for the pope," a reference to "kind of what Michelangelo used to have to do. Get a commission from the pope and then do his own stuff."

"This business is just lethal. That's why I'm doing it. For me. I couldn't bear it any longer," says Riegert, who says he gave himself "a gift" instead of just waiting for the next handout of a role in something that would feel like only a job.

Riegert says his body of work as an actor -- more than 30 movies from "Animal House" to "Traffic" -- may have been some help in attracting the cast, which includes Eli Wallach, Rita Moreno, Eric Bogosian and Isabella Rossellini. But he says their participation wasn't about doing favors; it was the chance "to be involved in good material."

These filmmakers' visibility as actors may also help get some publicity, but without big-budget marketing and promotion, most have to travel the country hawking their films at festivals, meet-and-greet screenings and drop-in visits to radio stations, and seeking any access where their core audience may be found.

All agree that getting their movie to the ticket buyers is even more difficult than raising the -- by Hollywood standards -- modest budget to produce it.

Actor-turned-filmmaker Campbell Scott received critical acclaim at festivals for this year's "Off the Map," which he directed, and "The Dying Gaul," which he produced, but getting his offbeat films into theaters has been tough. As he told The Post last spring: "No one wants to make these kinds of movies. Trust me. I have a good reputation. I meet with all these perfectly smart people at very good distribution companies. And they say to me, 'This is one of the best scripts I've ever read. There's no way I'm going to make it. I don't know how to sell it. Nothing happens!' "

Similarly, Reiser says distribution executives told him, "We really laughed and we really cried, but we don't know how to sell it." However, after a couple of months on the festival circuit, one executive, Bob Berney, president of HBO/New Line's newly established Picturehouse, was prepared to back Reiser's belief that the movie could and should play in theaters rather than go straight to DVD.

Berney says filmmakers who have struggled to get their films made are faced with "a whole new battle" when they seek distribution. They often encounter rejection, especially with personal projects such as these that don't fit into formulaic genres. "Some filmmakers understand it in advance; others are shocked and have no idea how strange and difficult and what a whole 'nother process it is."

Schroder, the onetime child star of "The Champ" and the sitcom "Silver Spoons," and currently starring on the Lifetime TV medical drama "Strong Medicine," financed the production of "Black Cloud" in partnership with Native American tribes, but then found major distributors uninterested. So he contacted the theater chains himself.

"Luckily, because of who I am and my credibility and name, I get to talk to people that probably a lot of small independent producers don't," he says, explaining how he went to the ShoWest movie industry convention in Las Vegas and "just started shaking hands and getting phone numbers and meeting people, and that really, really helped. Also it helped that they liked my movie." He achieved a two-stage 15-cities release in the fall of 2004 and spring of this year, before New Line released the DVD in June.

Last week, Estevez, whose film credits include "The Breakfast Club" and "The Mighty Ducks," wasn't worrying about distribution as he was too busy trying to ink other star names for his ensemble "Bobby" cast, which already includes Anthony Hopkins, Sharon Stone, Demi Moore and Elijah Wood. Estevez describes the film as a "100 percent independent project" that's about "the price we pay for getting rid of people who embody hope."

He credits the topic in part for keeping the project alive. "Much as I would try to forget the movie, I would be out at a function, at a party, on the street, meeting actors, agents, managers, producers and they would say, 'Hey, whatever happened to that movie "Bobby"?' So it stayed alive. . . . It was memorable and it wasn't something that anybody wanted to let go of. So kind of -- what's that line in 'The Godfather'? 'Every time I try to get out, they pull me back in!' It was as if there wasn't any escaping it. It was fate, perhaps," Estevez says.

Malkovich's film, "The Libertine," about the decadent 17th-century poet and Earl of Rochester, John Wilmot, reportedly had a rocky road that included losing financing because of a change in British tax laws and a casting merry-go-round (Malkovich, 51, got too old for the principal role, Johnny Depp was cast and then dropped out for personal reasons, then came back). Weinstein Co. has signed on to distribute the film in January.

Swayze in 1987 starred in the smash hit dance movie "Dirty Dancing" but still had to struggle for years to make "One Last Dance," written and directed by his wife. Having refused to compromise their dream in terms of its content, they then ran into the distribution roadblocks.

"We've always had a confidence that there was a huge dance audience out there . . . but we were trying to get distribution rights just at a time when everybody got paranoid. They were only looking for big studio movies or dark little festival movies," he says, explaining that he ultimately rejected the "bad" deals he was offered, to go directly to DVD. "The hard part is not letting yourself get beat down in the process. . . . We hung in because we felt we had something special to share with the world. Our movie hits that moment in time for all of us when we gave up on a dream but then got to realize and remember that it's never too late to rediscover that dream or make up a whole new one."

Paul Reiser and Peter Falk in "The Thing About My Folks," a father-son tale Reiser wrote that was years in the making.Peter Riegert co-wrote, directed and stars in "King of the Corner." He says the project was like giving himself a gift.Lisa Niemi and husband Patrick Swayze finally chose to take their pet project, "One Last Dance," direct to DVD, rather than compromise on its content.