In a research paper, scientists at Disney Research in Pittsburgh proposed a tactile rendering algorithm for simulating 3D geometric features on touch screens.
Using electrical impulses, the touch screen technology offers the sensation of ridges, edges, protrusions and bumps and any combination of those textures.
The researchers presented the technology at the ACM Symposium on User Interface Software and Technology in St Andrews, Scotland.
While Disney is not alone in developing tactile response touchscreens, its researchers said the traditional approach has been to use a library of ‘canned effects’, which are played back when someone touches a screen.
“This makes it difficult to create a tactile feedback for dynamic visual content, where the sizes and orientation of features constantly change,” said Ali Israr, an engineer with Disney Research. “With our algorithm, we do not have one or two effects, but a set of controls that make it possible to tune tactile effects to a specific visual artifact on the fly.”
The touch-screen devices can also receive tactile feedback relating to form and surface topography. If a user is exploring a 3D rendering or a navigational map, depth and elevation information would also be related through touch.
Environmental settings can also be rendered in real time, allowing users access to spaces and surfaces they may not typically have access to. Additionally, the technology could offer information to the visually impaired about their location, helping them to better discern their surroundings by touching the touchscreen.
A demonstration of Disney’s tactile algorithm, which uses electrical impulses to offer the sensation of ridges, edges, protrusions, bumps.
Disney said its computer algorithm consists of three main steps. The first calculates the gradient of the virtual surface in need of rendering; it then determine the ‘dot product’ of the gradient of the virtual surface and velocity of the sliding finger, and then it “maps the dot-product to the voltage using the psychophysical relationship”.
Called a ‘slope model’, the algorithm would combine with hardware to produce an electro-vibration-based friction display to modulate the friction forces between the touch surface and the sliding finger.
When a finger slides on a touch-screen object, minute surface variations are sensed by friction-sensitive mechanoreceptors in a person’s skin. The computer algorithm then modulates the friction forces between the fingertip and the touch surface to create the illusion of surface variations.
“We first determined a psychophysical relationship between the voltage applied to the display and the subjective strength of friction forces, and then used this function to render friction forces directly proportional to the gradient (slope) of the surface being rendered,” the researchers stated in a news release.
The researchers said a comparison study showed that users are at least three times more likely to prefer the proposed slope model than other commonly used models of tactile touchscreens.
“Our algorithm is concise, light and easily applicable on static images and video streams,” the researchers stated.
by Lucas Mearian, Computerworld