August 12, 2019

How InviziTrak Could Save You Tons of Time In Post

The laser based InviziTrak system completely eliminates removing camera markers in post.
Using pulsing lasers on a green screen saves hours removing camera tracking markers in post.

Recently at SIGGRAPH, I came across a new technology that could drastically reduce the amount of time it takes cleaning up green screen shots with camera tracking markers. You know, those marks that are needed for visual effects artists to gauge camera angle and depth for CGI? Since they usually appear as a different color, they have to be removed digitally before any meaningful CGI work can be keyed in. But with a new laser based camera system called InviziTrak, rotoscoping out your camera markers can be a thing of the past.

Lasers from Invizitrak pulse in sync with the camera to emit lazer tracking dots
Credit: Invizitrak

Simply put, InviziTrak is a series of lasers that are synced with a camera shooting at 48 fps. Lasers emit dots strategically placed onto the green screen as camera markers, but are pulsed at every other frame. The result is two separate footage streams, each a cinematic 24 fps, that can be broken out showing one channel to the director, and one channel to the visual effects supervisor. The end result is that visual effects artists don't have to rotoscope out any camera markers, but still can have them available for creating virtual backgrounds.

The idea came from filmmaker and visual effects supervisor Brendan Bellomo, who worked on the Oscar-nominated Beasts of the Southern Wild and Mike Hwang, a former SpaceX rocket engineer, who was working on a robotics servo controller for the animatronics. 

“I’ve supervised over 2,000 green screen shots and there are very few that wouldn’t have benefited from this kind of system,” Brendan says.

Talking with Brendan over the phone, he explained to me that he always wanted to do stuff in camera with high-quality green screen footage, but he wasn’t thrilled with tracking markers because they got in the way of getting a good, clean key. The markers also slow down post-production workflow due to rotoscoping them out to clean up the background.

That was the motivation for creating InviziTrak, using green laser dots on green screen for camera tracking.  The marker was initially going to be a different shade of green for the green screen (although it could be any color, really), but that lowered the quality of the matte. Hwang got the idea to intermittently project the alignment dots every other frame, as it was synced to a camera running at 48fps. Thus, you have high-quality tracks at 24fps, and no tracking mark removal.

By completely eliminating the need to use traditional tracking markers, on-set VFX supervisors can focus on the filmmaking process and VFX artists no longer need to remove tracking markers from green-screen or non-chroma key VFX plates.

Then, the pair added a timing sensor that genlocks the camera from either the ARRI or RED proprietary connector, or via HD-SDI. The sensor then transmits via a traditional style radio transmitter to the laser cube array to project the markers when and where needed.  The laser markers can then be adjusted to project to the side or top of the green screen, so they are completely behind the talent, thereby not interfering with their performance. They can also adjust the exposure, so it's all quite subtle. 

The system speaks four languages, camera, visual effects, lighting and grip. So it’s well suited to on set workflow. And it’s remote controlled by an iPad via separate wifi channel. 

The lasers are also firing according to their own clocks, so even with camera movement, or where it experiences a physical impediment, the system never loses sync with the camera track. Tracking markers can often blur during camera movement, but with InviziTrak, those markers remain intact, even during camera movements like whip pans.  InviziTrak also works on blue screen as well, and can support arbitrary object tracking, a variety of frame rates, and you can even dedicate one monitor to be tracking free, and one to be at a live keyer/tracker. That way, no one on set is distracted. 

Bellomo says that after their presentation at SIGGRAPH this year, they received major interest in the system from ILM, Digital Domain, and a host of Cinematographers who were in attendance. They plan to have a rental unit available within a few months and are looking for beta testers to shake out the technology. 

I gotta say, it makes a lot of sense. We're in the digital age now, where everything can be done with technology, and if you can cut valuable post time from doing grunt work like rotoscoping just to clean up your green screen plate, well that's going to translate to faster post times, and a healthier visual effects industry.

For more information and to maybe get in on that Beta Test, visit InviziTrak.com

Your Comment

2 Comments

Wouldn't the set of frames that see the tracking markers be spatially different than the frames that don't see the markers? So, I'm assuming the applications for this would only be for pretty slow camera movements, like the one in the demo video.

August 12, 2019 at 1:20PM

1
Reply

I'd imagine if it knows where frame 1 is and frame 3 is it can interpolate a pretty accurate position for frame 2.

August 12, 2019 at 4:28PM

2
Reply