Skyline” may look like a typical studio release, with its pricey marketing campaign, a major presence at Comic-Con and rollout on nearly 3,000 screens, even playing at Grauman’s Chinese theater. But making the low-budget sci-fi thriller look more like a studio pic may be Greg and Colin Strause’s most convincing visual effect yet.

After years of working on other people’s movies, the brothers behind Santa Monica visual effects studio Hydraulx (whose credits include “Avatar,” “300,” “The Day After Tomorrow,” “2012,” “Wanted” and Sony’s upcoming “Battle: Los Angeles”) decided to put their inhouse resources to the test and produce their own pic.

And the Brothers Strause, as they call themselves, were determined to make their alien-invasion actioner outside the studio system — at least as much as they could.

That meant raising development and production coin for the $10 million pic themselves by ponying up $3.5 million out of pocket and locking down the rest by preselling foreign territories.

Canadian distributor Alliance provided much of the upfront coin, while IM Global handled presales to territories including France, Italy, Thailand, India and Russia to recoup upfront production costs.

For the shoot, Hydraulx relied on its own post-production, editorial and camera departments, and custom-built certain lenses.

“We have every lens you could ever need to shoot a movie,” says Greg Strause.

The project wasn’t just shot inhouse — it was shot at one of their own homes, in a Marina del Rey apartment tower, with a story also designed to keep costs down. Plot revolves around a group of friends, played by “Scrubs’?” Donald Faison, Eric Balfour (“Six Feet Under”), David Zayas, Scottie Thompson and Brittany Daniel, who return to a loft after a night of partying only to discover they’re the lone survivors of an alien attack.

Overall, it took less than a year to develop the film and get it on the bigscreen.

“That’s a big departure from the way a studio works,” Strause says. “We essentially became the studio for the first half of the life of the project. It’s kind of like the studios operated in the ’40s and ’50s where you had the staff in place.”

The Strause brothers had been stepping up their efforts to helm more films after having co-directed the sequel “Alien vs. Predators: Requiem,” in 2007, for Fox. But “Skyline” “represents a huge change for our business because instead of being a strictly service provider, we’re delving into the

content-ownership game,” Strause says.

While other f/x shops have tried to produce their own pics, few outside of George Lucas and Industrial Light & Magic, and Digital Domain (with “Secondhand Lions”) have been successful.

“All of the visual effects company have been trying to do this for a long time,” says Jeff Barnes, co-founder of CafeFX and a production exec on “Pan’s Labyrinth.” “My hat’s off to them.”

In order to send “Skyline” to the megaplex, however, the Strause brothers still needed help from the studio system.

After screening the film for Brett Ratner, with whom they worked on “X-Men: The Last Stand,” Ratner took the pic to Ryan Kavanaugh’s Relativity Media. Kavanaugh quickly agreed to release it through the company’s Rogue banner, whose films are released by Universal.

The studio paid for the pic’s marketing budget of more than $20 million, according to some sources, whose campaign relied heavily on the concept and imagery of aliens attacking Los Angeles.

Relativity saw the pic as a chance to release its own “Cloverfield” or “Paranormal Activity,” low-budget pics with long legs at the B.O.

As Ratner tweeted while championing the pic, “The cost of ‘Skyline’ really doesn’t matter! Its just amazing what they did with what little they had!!”

“In the end, a studio is really betting on the director and filmmakers,” says Relativity prexy of worldwide production Tucker Tooley. “This structure allows the studio to give a lot more flexibility to the creative talent.”

While the Strause brothers feel they’re been able to reap the creative rewards of going solo, the financial benefits could soon follow.

Since its release on Nov. 12, the film has earned $13.2 million domestically, and is already generating solid numbers overseas, with nearly $11 million, including more than $5.3 million from Russia alone.

While it remains to be seen how much the brothers will make after those costs are recouped by Universal, they retain ownership, including franchise rights, allowing them to make a sequel, videogame or other property based on the original film.

Also, as part of an exclusive content deal between Relativity and Netflix, the pic will be one of the first to bow on the movie rental service next year after its DVD release. Universal will handle homevideo distribution.

“If foreign territories perform well, there’s going to be a lot of pressure from those guys to make a second one,” Strause says. “If the foreign buyers hate the script, then you don’t get to make it. Those territories want to know that you’ve got it figured out.”