Omnidirectional treadmills come in three flavors (left to right): torus treadmills, spheres, and tiles.

While The Matrix movies taught us that true VR may require direct interaction with our brains, physical systems still have much to offer. Exploring virtual environments by walking or running is a useful tool in training soldiers, and emergency workers. The first documented ODT in 1996 was built for the US Army. ODTs in entertainment would allow video gamers to immerse themselves in the action. When combined with haptics and telepresence, ODTs could provide the means of creating virtual work environments, allowing researchers to explore dangerous or remote locations through the use of robots. The bottom of the ocean or the surface of Mars could be accessible through VR technology.

Small Torus Treadmill:

The first ODTs were multiple treadmills lashed together into one bigger treadmill. These torus treadmills (named for the shape) combine motion in the X and Y axes to provide universal movement. In 1996, the US Army commissioned a small torus treadmill with a harness to provide feedback forces. The University of Tsukaba (Japan) followed suit in 1999. In the last few years Cyberwalk, an EU project located in Germany, built the largest torus treadmill: 6 meters by 6 meters with 20 square meters of active area. Cyberwalk claims it can scale the treadmill to almost any size, but that the 6×6 platform is the minimum for a truly immersive walking experience. Their ODT uses a markerless visual tracking system to match treadmill movement to the user’s walking. Cyberwalk teamed up with the Swiss Federal Institute of Technology to provide a virtual tour of the lost city of Pompeii in 2008.

Cyberwalk Torus Treadmill

Cyberwalk Exploring VR Environment

The next style of ODT isn’t really a treadmill at all. Virtusphere is a large metallic sphere on casters inside of which you can walk around freely. Unlike other ODTs, the sphere is a passive system – the users own weight and movement rotate the surface beneath them. According to the website, the sphere is easy to assemble and disassemble, uses ultrasound to track motion, and has a head mounted display to track point of view. While there is no harness to provide force feedback, the casters under the sphere could eventually be motorized for that function. Of all the ODTs, Virtusphere is my favorite, and I’m excited by the level of VR interaction displayed in their videos. The company was recently featured on the ABC reality show Shark Tank and could see a boost in interest even though the “Sharks” did not invest.

VirtuSphere Instructional Video (Russian)

VirtuSphere on SharkTank (at 23:00)

While torus treadmills and walking spheres would require setup and installation, the last ODT could be adopted almost anywhere. Circula Floor is a series of four motorized tiles that move into your walking path. Each tile has a unique set of wheels underneath that allows it to translate on a floor in any direction. With four tiles, you are always walking on two while the others are lining up to your eventual path. Using a laser range finder and an ultrasonic position sensor, the tiles can anticipate where to be, but their movement seems disappointingly slow. Still, the University of Tsukaba, creators of Circula, have a long history with ODT and they may be able to increase its response time as they develop the technology.

Circula Floor

Walking through a virtual world is going to be an amazing experience once we get the technology up to speed. I prefer the Virtusphere approach because a passive system would allow almost any type of motion (walking, running, rolling), though it would have to be built much larger to simulate a flat walking surface. The other systems have their merits and I would be happy with any technology that can be easily adopted for multiple uses such as gaming, virtual exploration, and training. No matter which physical system is paired with the sensory side of VR we will likely have to wait several more years before virtual reality is ready for market.

[photo credit: Cyberwalk, Virtusphere, University of Tsukaba]

[video credits: Cyberwalk, Virtusphere, ABC, University of Tsukaba]