Disney researchers have developed an algorithm for tactile rendering of three-dimensional (3D) features and textures. By altering the friction encountered as a user's fingertip glides across the surface, the Disney algorithm creates a perception of a 3D bump on a touch surface without having to physically move the surface. "If we can artificially stretch skin on a finger as it slides on the touchscreen, the brain will be fooled into thinking an actual physical bump is on a touchscreen even though the touch surface is completely smooth," says Disney researcher Ivan Poupyrev. During testing, the researchers used electrovibration to modulate the friction between the sliding finger and the touch surface with electrostatic forces. In addition, the researchers created and validated a psychophysical model that closely simulates friction forces perceived by the human finger when it slides over a real bump. "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," notes Disney's Ali Israr. The researchers are presenting their work at the ACM Symposium on User Interface Software and Technology this week in St. Andrews, Scotland.