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The Joy of Virtual Sets

The USS Enterprise from Star Trek: The Next Generation had its famous holodeck, where the giant starship's crew could escape from the routine of shipboard life for a few hours by relaxing inside a computer-generated virtual world. While technology hasn't progressed that far (fortunately, we do have three centuries to get there!), using virtual sets for a video production can seem almost like the next best thing, transforming a garage, basement or other relatively cramped shooting location into an expansive alternative location, if not universe.

Virtual sets provide several advantages for video production on a budget and with limited shooting schedule. Not only do you not have to build (or travel to) numerous locations, but also the production is cheaper and quicker.

Of course, producers use virtual sets on projects with giant budgets as well. George Lucas's Star Wars prequels and films such as Sin City, 300 and Sky Captain and the World of Tomorrow all feature vast arrays of actors and extras surrounded by ginormous virtual sets. This is in part to avoid the expense of physically building those complex settings in real life. Increasingly, virtual sets are in use for live productions, as we'll discuss further into this article.

But odds are that your productions are a bit simpler than these shoots. This is particularly true if you build the shoot around a fairly short TV commercial or online YouTube-style clip.

Unlike a real set or location, where the entire set needs to have even and careful lighting, you need a minimum of lights for virtual sets: you need to light only the talent and the green (sometimes blue) chromakey backdrop. For those Star Wars-sized virtual sets, that still may be a lot of lighting. But for many applications, the talent can remain in one or two basic positions (sitting, standing, occasionally walking into or out of a shot). Lights can often remain in one location on a single set, even though the finished product will end up looking as if you shot your the talent from numerous camera angles on multiple sets.

Quiet on the Set

A shooting set for greenscreen can easily be a garage or basement if your goal is video blogging or other DIY-style video productions. In any case, greenscreens and chromakey allow you to mat out lights, booms, cables and other objects in the corners of the shot afterwards. This makes virtual sets a remarkably forgiving environment, particularly on the small screen. Virtual sets seem particularly suited to web-based productions; since they're computer graphics to begin with, they typically compress well when rendered to an online video format such as Flash.

While lighting the talent is obviously a matter of taste and will vary based on the desired look, some general rules apply. It helps to light the actor and backdrop as separate elements. The usual rules regarding avoiding clothes that moiré apply. A hair light (possibly with an amber-tinted gel clipped onto the light) is often useful to further separate the talent from the backdrop.

Position the talent several feet in front of the green- or bluescreen to reduce the reflected green spill onto the talent. This distance also helps to defocus the backdrop, reducing visible wrinkles and other flaws in the backdrop, which can vex some chromakey programs. Make sure to light backdrop as evenly as possible.

The type of backdrop will vary according to your production needs. The portable greenscreen backdrops produced by manufacturers such as Photoflex and Botero are fine for many small productions, but they do have one limitation: Because they don't reach the floor, they could limit the types of virtual sets and shots you can do, since these backdrops rule out full-length shots of the talent.

Unless portability for location shoots is a goal, it is better to get the biggest hanging greenscreen that will fit your studio wall (check out websites such as Imagewest.TV for ideas). Or consider building a permanent greenscreen cyclorama in your studio, using products such as those manufactured by Pro Cyc, Inc. Even this type of backdrop does not require a dedicated room. In fact, lights and cables will be more of a deterrent than a green-painted wall alone for keeping other family members off the set.

To Ultra - and Beyond!

Once you've shot your talent on your greenscreen soundstage, then the real fun begins. You can import the footage into your nonlinear editing program (NLE), select the best takes and then it's time to start compositing the talent into their virtual environments.

Many popular NLE programs contain built-in chromakey applets, and these can often work fine for many projects. There are numerous web-based merchants, such as the appropriately named Virtualset.com, which provide digital images for download or on disc for importing into keying applets. There are also stock photos or video shot on location which you can use for a backdrop. A digital backdrop such as Digital Juice's popular series of Jump Backs can also be an effective backdrop for a talking head-type video.

But for many, virtual sets are synonymous with Ultra 2 from Adobe. Currently a Windows-only application, Ultra 2 is a remarkably quick, powerful and forgiving keying program, with a number of virtual sets sold both by Adobe and by aftermarket manufacturers. For those using Ultra or considering it, here are some suggestions to make the most of the product.

Many of the virtual sets available for Ultra 2 combine motion tracking, which allows for some incredibly sophisticated camera moves. Several of the sets combine these tracking moves with a rapidly-changing sense of scale, resulting in the viewer's seeing the camera pan over virtual cityscapes or even outer space, before arriving at the actor, for a bravura establishing shot. As an example, Archives, one of the Ultra sets in Adobe's Virtual Set Library #4 features a master shot in a virtual set that looks as big as the Library of Congress. The camera begins by swooping from the second floor of the archive set, down to the talent on the first floor. From there, you simply cut to closeups and medium shots of the talent as appropriate.

Ultra makes shooting these kinds of shots simple. On the soundstage, you lock the camera down on a stationary tripod, the talent stands in front of the greenscreen and you record a full-length shot of the talent. (Hence the need for a greenscreen that goes from floor to ceiling, as we mentioned previously.) You then load this relatively simple shot into Ultra, choose the virtual set, set the chromakey to mask the greenscreen and then - voila! - the program does the rest, manipulating the size and placement of the actor in relation to the sweeping virtual camera moves.

While some sets for Ultra contain equally dramatic closing shots, not all do. But it's possible to generate some pretty nifty pullbacks by reversing an opening shot. For example, the above-referenced shot of the talent standing in the gigantic Archives virtual set could be reversed, so that the camera starts on the actor and tracks outward to the top of the rafters (perhaps ending on a fadeout to the closing titles). To do this takes some practice and trial-and-error, but the first step is to reverse the footage of the actor standing (or sitting) in front of the greenscreen set via your favorite NLE, then import this footage into Ultra. Once in Ultra, adjust the clip's starting time and offset into the scene, and output a trial clip of the composited shot. Import the completed clip into your NLE's timeline, and then reverse it and check out the results. It may take a couple of tries to get it right, but it can be worth it. Ending a video production with a reverse of its opening shot can add a powerful sense of symmetry, as the camera starts with a closeup of the talent, then dollies back to infinity.

Many chromakey programs allow for shadows to be computer-generated behind the talent. Some, such as Ultra, can also add shadows to the floor of a virtual set as well. I often tend to crank these shadows in a slightly more exaggerated fashion than I would prefer to see shadows on a brightly-lit real-world television set, simply because the shadows subliminally help to meld the actor into his virtual setting.

Once you have rendered a shot in a program such as Ultra and inserted it into the timeline of an NLE, it's possible to manipulate it much further. Many of Ultra's stock sets have virtual television monitors built into them. I often insert a static title card or website logo into these, and then insert B-roll footage "into" these monitors by scaling it to fit afterwards in my NLE. This allows for a much more rapid cutting of images than the Ultra program itself allows. (You may need to use your NLE's garbage matte applet if an actor's forearm crosses a monitor or if the monitor has curved, rather than flat, corners.)

Whatever program or applet is used to generate the virtual set, you can often add additional realism and a nifty cinematic look. You can process a shot using a program such as Red Giant's Magic Bullet Looks software. Magic Bullet Looks' built-in Misfire applet can also add plenty of atmospheric grunge to an otherwise pristine virtual set, in the form of scratches, dirt and other cinematic funk, adding significantly to the sense of verisimilitude.