Meet Me Half Way: Concerted Physical and Virtual World Manipulations for Effective Haptic Feedback in VR

Passive haptic opportunities are scarce because they require the precise alignment of the virtual object with a physical object. Increasing the number of haptic opportunities can be done by moving the physical object to place it in alignment with the virtual object, i.e., through physical redirection. The physical object is moved with a robot called an encountered-type haptic device, or ETHD. Another option is virtual redirection, which manipulates the virtual object with which the user interacts with the virtual environment in a way that indirectly changes the user's physical motion to synchronize the physical and virtual contacts. This paper demonstrates that virtual and physical redirection can complement each other effectively. Indeed, the ETHD can reduce the physical to virtual gap that virtual redirection has to bridge, making the virtual redirection less noticeable. Conversely, virtual redirection can help synchronize the virtual and physical contacts when the ETHD fails to arrive at the needed position. A user study (N = 8), in which participants were asked to tap a virtual disk using a handheld stick, recorded the amount of physical and virtual redirection needed to synchronize the physical and virtual contacts. The results confirm that the faster the ETHD, the larger the physical redirection, and the smaller the virtual redirection needed. Furthermore, the ETHD provided sufficient reduction of the initial physical to virtual gap for the virtual redirection distance to remain below detectable thresholds that were measured by prior work.