The front rooms haven’t changed much since 28-year-old “Star Trek” fan Rob Caves inherited his grandmother’s house in Altadena, Calif. Curio cabinets and ’70s-style furniture give the impression that an old lady lives here.

But in the back, it’s the 24th century.

There Caves has assembled a makeshift studio for his “Star Trek” Web-only spinoff series “Hidden Frontier.” A hand-painted greenscreen covers one wall, against which two actors dressed in “Star Trek: The Next Generation” uniforms discuss their same-sex relationship.

“There’s never been a gay character on ‘Star Trek,'” says Caves. ” ‘Star Trek’ has always been about pushing social boundaries and portraying things that might be a touchy subject now, but in the future, it’s no big deal.”

Caves is part of the legion of “Star Trek” fans taking advantage of advances in desktop filmmaking to create their own fan films. For many, that first taste of filmmaking leaves them itching to go pro — and using their fan films as a stepping-stone.

They may be in for a rude encounter: “We greatly admire and respect the passion which fans have for ‘Star Trek,’ but CBS Paramount’s trademark rights and the intellectual properties related to ‘Star Trek’ must always be protected from unauthorized use,” says John Wentworth, exec VP of communications for CBS Paramount TV. “Our policy is to pursue our legal options when those rights are determined to be violated by anyone.”

Fans feel safe as long as they don’t charge auds to view their films, but as long as the threat of legal action obstructs any way of recouping their investment, those making underground “Star Trek” pics will abandon ship as they run out of funds.

This is the seventh and final season of “Hidden Frontier.” “Sprint PCS is trying to talk to Paramount right now to see if they can license this for their phones,” says Caves. After nearly 50 episodes, each costing roughly $500, Caves hopes the “Hidden Frontier” fans will follow him to his next project, an original sci-fi story.

In Finland, the team behind the feature-length parody “Star Wreck: In the Pirkinning” gave the movie away for free (more than 4 million downloads) but made enough selling T-shirts and other tie-ins to finance an original sci-fi feature, “Iron Sky.”

“We’ve been doing a lot of shitty jobs in our lives,” says director Timo Vuorensola. “Now we finally have time to do something that we really like.”

James Cawley, a professional Elvis impersonator based in Ticonderoga, N.Y., re-created the USS Enterprise sets for his “New Voyages” Web series. “New Voyages” seeks to complete the original series’ five-year mission (NBC canceled skein after its third season). “I have a career. This is a very expensive hobby at this point,” he says — an estimated cost of $70,000 per episode.

“New Voyages” racked up more than 30 million downloads for its latest episode — and Cawley hopes its popularity would bring Par onboard.

Doug Drexler, a veteran “Star Trek” designer who creates visual effects for “New Voyages,” views the project as an ideal training ground for filmmaking talent. “From show to show, you can see the quantum leap in the quality of work. I see this evolving into a production company that will do other stuff,” he says. Drexler was impressed enough by Jack Marshall, who directed the “New Voyages” pilot, that he recommended him for a job on “Battlestar Galactica.”

“If you went to Paramount over the last 25 years, in any given department you would find Trekkies who gravitated to the studio that produces the movies and TV shows,” says “Trekkies” docu director Roger Nygard.

Gabriel Koerner, one of the most enthusiastic fans profiled in the docu, has parlayed his CG spaceship models into work as an Emmy-nominated digital artist on “Star Trek: Enterprise,” “Battlestar Galactica” and “Lost.”

“It’s one of those funny things where my fan-filmmaking efforts got me my career in the first place, and now my career is eating up too much of my time to finish my fan film,” Koerner says.