Usability evaluation of two simple methods for representing heaviness of virtual objects

Perception of heaviness of virtual objects can play an important role in improving the user interaction within virtual environments. It could especially prove beneficial in applications, such as virtual assembly and medical surgery, which largely consist of selection, manipulation and grasping tasks. In order to achieve weight perception in virtual environments, haptic devices have been commonly used. However, they are hard to incorporate into immersive virtual environments (IVEs) due to their functional complexity. This paper evaluates the usability of two simple interaction approaches using a light-weight finger-tracking device. One method is based on the distance between tracked fingers and the thumb, the other uses the intensity of pinching fingers during grasping gestures providing tactile feedback. Building on previous results of evaluating the performance by measuring the Weber fraction, in this paper, we further evaluate usability of our methods as a function of the overall workload placed on the user while performing a sorting task based on perceived weight. The results confirmed that the performance of both methods for the sorting task is comparable and both methods allow distinguishing between the heaviness. However, the experienced workload was higher for the pinch based compared to the distance based method and participants had higher confidence in the distance based method