Detectability of ETHD Position and Speed Redirection for VR Haptics

Abstract An encountered-type haptic device (ETHD) moves a physical object to align it with the virtual object with which the user of a virtual reality application makes contact, providing haptic feedback. One limitation of ETHDs is their limited reachability due to mechanical constraints. One approach to extending the reachability of an ETHD involves redirection, achieved by altering the pose of the user’s body, hand, or handheld prop in the virtual world. While previous studies have quantified the detection thresholds of redirection in the context of stationary objects, ETHD’s present the opportunity and the need to study redirection in the context of dynamic objects. This paper presents a user study $(\mathrm{N}=25)$ with two experiments aimed at investigating whether dynamic object properties, such as direction and speed, significantly affect redirection detection thresholds. The first experiment finds that the mere presence of dynamic objects does not decrease the detection threshold. Consequently, previously measured detection thresholds remain applicable for ETHD reachability extension. However, the second experiment unveils a crucial relationship between the speed of dynamic objects and the original reachability of the ETHD. Although the virtual object can move $15 \mathrm{~cm} / \mathrm{s}$ faster than the ETHD, this increase in speed is insufficient to compensate for the extended reachability enabled by the detection threshold.