Love it or hate it, CNN's use of Star Wars-style "holograms" on election night was one of the most striking pieces of TV magic to date. But as impressive as it was for Chicago-based reporter Jessica Yellin and entertainer will.i.am (of the hip-hop band Black Eyed Peas) to "beam in" to Wolf Blitzer's New York Election Center for live "face-to-face" interviews, the way CNN made it happen was even more astounding. Here is the science behind the magic.A DREAM REALIZED
|will.i.al beams in to CNN's New York studios. |
The driving force behind CNN's holograms is David Bohrman, the network's senior vice president and Washington bureau chief. For 12 years, Bohrman has dreamt of improving on live remote interviews; typically executed using satellite-linked guests based in other physical locations. His idea is akin to the famous "Star Wars" scene in which a 3D talking, moving hologram of Princess Leia is projected by the droid R2D2.
"I've basically been a crazy mad scientist, trying to get this done," Bohrman told CNN anchor Wolf Blitzer on CNN following the election. "This year we pressed really hard, and about three months ago we launched into developing it, and it ended up working."
To make it work, CNN (led by Washington Senior Video Producer Chuck Hurley), Ran Yakir from Israel-based graphics company Vizrt, and freelance broadcast engineer/consultant Jason Odell brought together several different broadcast technologies. These were drawn from Vizrt, SportVU, Shotoku Broadcast Systems, Thoma and Fujinon. "It was a very complex project," Odell said, both in scope and because "there were so many different players, of which CNN Engineering was the lead."HOW IT WAS DONE
Yellin and will.i.am's interviews were shot in two temporary studios, built inside a massive tent in Chicago. The inside of each studio was home to a 220 degree semicircular chromakey green stage. Inside this space—a.k.a. the "Transporter Room"—were 35 HD "machine vision" CMOS cameras. Spaced six inches apart around the 220 degree arc and pointing towards the space's center, these 2D cameras were positioned to provide multiple angles of the subject; images that could then be composited to create the illusion of a 3D whole. "It is akin to shooting QuickTime VR [virtual reality], except that the cameras were pointed in at a subject, rather than out to capture a 360 degree," said Goshen, Vizrt's director of usability.
A diagram of the Vizrt-SportVu workflow.
So how did this create a 3D image? Hurley described the process as simply taking existing chroma-key technology to extremes. "Weathermen have been standing in front of green screens for years now, but that's [with] one camera," Hurley said in an interview on CNN.com. "Now we can do that times 35, so you can send all the way around the subject."
Adds Odell, "From these 35 fixed cameras we can now derive an infinite number of viewpoints."
In New York, CNN used positional tracking camera pedestals and a jib from Shotoku Broadcast Systems. The goal was to bring 3D positional data back to Vizrt Viz IO camera tracking software (part of Vizrt's Virtual Studio suite).
"Every moving part of our pedestals and jib are equipped with high resolution encoders," said Naoki Ebimoto, president of Shotoku (USA) Inc. "This data is calculated instantly so that we know precisely where the camera is located and looking in real time without any delay." Positional tracking signals of CNN's handheld cameras were fed to the virtual studio computer with 3D data captured by IR cameras in the New York studio, using Thoma's Walkfinder technology. All this data was processed by Viz IO and supplied via fiber to Chicago.
Back in the Transporter Room, the tracking data told the Vizrt Virtual Studio software which two cameras should be accessed to provide the right 3D perspective for creating the hologram. Next, using a Viz Engine plug-in originally created by SportVU to show where players are on a game field, a 3D electronic model of the person being shot (Yellin or will.i.am) was rendered in Viz Engine. On top of this model was laid the video texture captured by the cameras.
"The in-between frames [those locations which do not correspond to a single camera view]—both in shape and color—were smoothed out by the plug-in of SportVU in Viz Engine," said Goshen.
Once the final image was ready, it was sent back to New York via fiber, so that the local and remote feeds could be blended to create the hologram illusion. The result: Holograms on television, live!NOBODY THERE
Two points worth noting: First, Wolf Blitzer didn't actually see the hologram standing before him in the studio. Instead, he looked in the direction of a 'red dot' on the studio floor while watching the combined play-out on a monitor.
Second, the Star Wars-like blue edging that surrounded Yellin and will.i.am was not an artifact like the ones around Princess Leia in the movie. (That sequence—to which CNN's effort has been constantly compared—was entirely faked and never done in real time.) Instead, CNN deliberately added the blue edging during production to alert the viewers that it was an effect, not an in-studio live body.
One of the most interesting challenges of CNN's hologram effect was the time delay between Chicago and New York. The problem was not the speed of the fiber-optic link, but rather the time it took for the Vizrt/SportVU system to process the Shotoku/Thoma position data and create the right 3D hologram image.
"It initially required four seconds for this to happen, but we got it down to three," said Odell. "Still, this processing time meant that the director in New York had to decide which camera shot she wanted next, bring it up on his Preview channel and then send us that data. Once we had it, the 3D image was created and sent back as a full HD signal; only then could she take to the next camera shot."
Even with three months' lead time, CNN Engineering and its partners had to work full-out to make the hologram effect available for the election day broadcast. Thanks to their efforts, the system "basically worked perfectly," said Odell. Still, he would have preferred to have more time to iron out the bugs. "If we had, maybe we could have had the interview guest directly on top of the 'red spot' in Blitzer's studio at all times, where they were supposed to be."
Will CNN's hologram effect become a staple of broadcast television? Odell thinks so. "I think people will demand it in sports," he said.
But Goshen isn't sure. "It is probably overkill for projects that are smaller than U.S. elections," he said. One problem is the degree of training that camera operators require to ensure that the tracking system functions properly. "You can't expect freelancers to come in and know how to do this," he said.
"We'll see," Bohrman told Blitzer during their post-election chat on CNN. "But television evolves, and how we do things evolves, and at some point—maybe it's five years or 10 years or 20 years down the road—I think there's going to be a way that television does interviews like this because it allows for a much more intimate possibility for a remote interview."