On ER, a helicopter struggles to land on a rooftop during a violent storm. In Helen of Troy, thousands of Greek ships attack the city of Troy, and the oversized wooden horse is wheeled through the gates of the city. The camera flies into the ancient city of Rome in Spartacus, or over the Montecito Hotel in Las Vegas. These are just some of the “virtual backlots” that Stargate Films has created over the last six or seven years. The facility has been gradually increasing its ability to create photoreal locations – and place actors within them. “The key has been not to overextend our capabilities,” says founder/CEO Sam Nicholson. “We’ve been very selective about the people and productions we work with and very careful about not dealing in quantity.”

Now, says Nicholson, the Virtual Backlot is quickly gaining momentum. Thanks to Moore’s Law, creating truly photoreal imagery isn’t as daunting a feat as it used to be, and Stargate’s virtual backlot is becoming a staple in Hollywood television shows. The Montecito Hotel set in the neon frenzy of Las Vegas? That’s a Stargate Films creation. Placing actors on "location" in Chicago and Boston for ER and Crossing Jordan? Also a Stargate Virtual Backlot feat.

Nicholson says Stargate is working on 22 television shows, including 14 pilots. “We can now do things in 3D that were considered impossible ‘ and bring them to life in a TV schedule,” he says.

Stargate's virtual backlots are not to be confused with photoreal matte paintings. Actors interact with these virtual environments – they get on and off a Moscow subway, for example. And, with the exception of CG fabrications such as the Montecito, the sights you see — from the Eiffel Tower to the London Tower – are all real. The virtual backlot library houses about 1,000 hours' worth of London, Paris, Tokyo, Washington D.C., New York City, Los Angeles, Las Vegas and other locales.

These are no ordinary stock footage shoots. The technique depends on the creation of a 360-degree immersive environment. The Stargate Films cinematographer (often Nicholson himself) goes to locations with several cameras including a Sony HD F-950 recording to HDCAM SR tape and, for tight spots, the Panasonic 24P HPX-2000. Each camera is outfitted with a nodal camera head that enables pan or tilt with no perceptual shift. In other words, a tilt from the top to bottom of the Eiffel Tower or a full 360-degree pan from the top of the London Tower fills out this virtual universe. “That becomes photographic data, essentially,” Nicholson explains. “Then you can, ideally, texture wrap onto 3D surfaces. So you’re looking at a combination of 3D modeling and photographic textures.”

Once the photography is done, the HD shots are stitched together using RealViz Stitcher, creating panoramas. The result is a very high-resolution immersive environment created out of up to 30 “panels,” each of them up to 16 mega-pixels in resolution. “Stitcher gives us a polygonal mapping tool,” explains Nicholson. “The photographs aren’t literally stitched together like you’d do in Photoshop, but it’s a series of frames in a virtual box, a kind of virtual QuickTime.”

To this high-res panorama, Stargate Films adds elements including digital still photos and 3D elements that, says Nicholson, take these virtual backlots “to the extreme, with interesting adjustments.” A virtual backlot of Moscow’s Red Square, for example, blends live-action elements shot with the Sony F950 with 20 high-res digital stills mapped onto the same model.

The 3D CGI objects play a special role in selling the immersive environment. “Imagine you’re sitting in a 360-degree IMAX theatre with 3D objects between you and the screen, and you’re the actor,” says Nicholson. “The world exists as a 2D backdrop, and as you get closer, you start seeing depth. The closer the objects are to the camera, the more important it is that they be 3D.”

With a virtual backlot at their disposal, directors can create their own shots. “I can pan from the Champs Elysee to the Eiffel Tower,” says Nicholson. “But another filmmaker might want to move from the top of the Eiffel Tower to the River Seine.”

The final – and crucial – touch to this “blended reality” is lighting. With global illumination, the environment lights the object and that, in turn, is how the cinematographer lights the actors. “Probably one of the biggest black arts is how to light the actors so they really look like they’re in the environment,” he says. One of Stargate's 16 visual-effects supervisors always attends the live-action shoot to make certain that it’s lit properly for blending with the virtual backlot. “You need at least a visual-effects supervisor with a keen sense of lighting on the set and a DP who is very understanding and comfortable shooting green screen,” Nicholson says. “It’s a combination of direct light sources and also positive and negative reflective surfaces.”

Stargate uses Alias Maya 7 to extract the lighting map from the environment, which then becomes the lighting map for any 3D object in the environment. Nicholson notes that the virtual backlot can also use 2.5-D elements by multi-planing 2D objects, cutting them out and painting the background behind them.

Stargate Films is now working on expanding the number of virtual backlots available to directors. Though the library is fairly extensive, there are many more cities, monuments and environments to shoot. They’re currently shooting all over Los Angeles to capture the elements required for a virtual backlot to support Raines, a procedural crime TV pilot with a healthy dose of the supernatural, for director Frank Darabont. “We’re doing time-shifting during a scene, so it’s changing from day to magic hour to night in the middle of a shot,” says Nicholson. “In many instances, because of Virtual Backlot, you don’t need locations or sets. And it looks exactly like you’re really there.”