Foggy screens are usually an annoyance, but fog screens – where images are projected onto a fine mist – could open up the possibility of interactive holograms and free-floating displays. To make those projections a bit clearer, a team at the University of Sussex has found a way to make shape-shifting fog screens that can keep objects in focus and let multiple users work together.

The biggest complaint with existing fog screens, like DisplAir and MisTable, is usually the visual quality. As impressive as it can be to see images floating in mid-air, they can't display in high resolution because the fog scatters light in different directions, meaning pixels often bleed into each other, and the brightness can be patchy across the surface.

Dubbed MistForm, the Sussex team's creation tackles those problems by changing the shape of the screen while it's being used. Like other systems, the screen is made up of a thin fog layer, surrounded by "curtains" of air to keep it stable. A flexible pipe releases the fog from above, and that pipe is actuated to push the screen, or parts of it, back and forth within a range of 18 cm (7 in). The screen itself is about the size of a 39-in TV.

Using Microsoft's Kinect, the system can track a user's hand movements and bend the fog screen accordingly, so that everything is always in focus – a particular challenge in making virtual 3D objects look believable. Individual sections can be curved inwards or outwards too, letting multiple users either work together or separately.

For collaboration, the screen can bend around both people in a concave shape, giving them a bigger area to work with. On the other hand, if they don't need to see what the other is up to, the fog screen can take on a triangular shape and wedge between them, so each person effectively has their own display.

To keep images relatively clear, Mistform uses the Kinect, a head-mounted device called OptiTrack, and machine learning algorithms. By tracking where the user's head and hands are with Kinect and OptiTrack, the algorithms can then figure out just how to stretch and distort the images on the screen to counter the uneven surface of the fog. The result is, according to the team, a display that stays in focus from wherever the user or users are standing.

"With other 3D display technologies your eyes need to focus on the display surface, even if you see an object "popping out" of the screen," says Diego Martinez Plasencia, co-author of the study. "If you then try to touch it, your eyes will need to focus either on your hand or on the display, which soon can lead to eye fatigue. MistForm can adapt to these scenarios, moving the display surface so that both the object and the hand remain comfortably visible. With this kind of technique, we can provide comfortable direct hand 3D interaction in all the range your arms can reach."

The study was published online and the team will demonstrate MistForm this week at the Computer-Human Interaction (CHI) conference in Denver. The shape-shifting fog screen can be seen in action in the video below.

Source: University of Sussex