Grabbing at an angle

This paper investigates the pinch angle as a menu selection technique for two-dimensional foldable textile controllers. Based on the principles of marking menus, the selection of a menu item is performed by grabbing a fold at a specific angle, while changing value is performed by rolling the fold between the fingers. In a first experiment we determined an upper bound for the number of different angles users can reliably grab into a piece of fabric on their forearm. Our results show that users can, without looking at it, reliably grab fabric on their forearm with an average accuracy between 30° and 45°, which would provide up to six different menu options selectable with the initial pinch. In a second experiment, we show that our textile sensor, Grabrics, can detect fold angles at 45° spacing with up to 85% accuracy. Our studies also found that user performance and workload are independent of the fabric types that were tested.