Many illusion and interaction techniques in Virtual Reality (VR) rely on Hand Redirection (HR), which has proved to be effective as long as the introduced offsets between the position of the real and virtual hand do not noticeably disturb the user experience. Yet calibrating HR offsets is a tedious and time-consuming process involving psychophysical experimentation, and the resulting thresholds are known to be affected by many variables—limiting HR’s practical utility. As a result, there is a clear need for alternative methods that allow tailoring HR to the perceptual boundaries of individual users. We conducted an experiment with 18 participants combining movement, eye gaze and EEG data to detect HR offsets Below, At, and Above individuals’ detection thresholds. Our results suggest that we can distinguish HR At and Above from no HR. Our exploration provides a promising new direction with potentially strong implications for the broad field of VR illusions.

Hand redirection is effective so long as the introduced offsets are not noticeably disruptive to users. In this work we investigate the use of physiological and interaction data to detect movement discrepancies between a user's real and virtual hand, pushing towards a novel approach to identify discrepancies which are too large and therefore can be noticed. We ran a study with 22 participants, collecting EEG, ECG, EDA, RSP, and interaction data. Our results suggest that EEG and interaction data can be reliably used to detect visuo-motor discrepancies, whereas ECG and RSP seem to suffer from inconsistencies. Our findings also show that participants quickly adapt to large discrepancies, and that they constantly attempt to establish a stable mental model of their environment. Together, these findings suggest that there is no absolute threshold for possible non-detectable discrepancies; instead, it depends primarily on participants' most recent experience with this kind of interaction.

Visuo-haptic illusions are a method to expand proxy-based interactions in VR by introducing unnoticeable discrepancies between the virtual and real world. Yet how different design variables affect the illusions with proxies is still unclear. To unpack a subset of variables, we conducted two user studies with 48 participants to explore the impact of (1) different grasping types and movement trajectories, and (2) different grasping types and object masses on the discrepancy which may be introduced. Our Bayes analysis suggests that grasping types and object masses (≤ 500 g) did not noticeably affect the discrepancy, but for movement trajectory, results were inconclusive. Further, we identified a significant difference between (un)restricted movement trajectories. Our data shows considerable differences in participants’ proprioceptive accuracy, which seem to correlate with their prior VR experience. Finally, we illustrate the impact of our key findings on the visuo-haptic illusion design process by showcasing a new design workflow.

Many interaction techniques in virtual reality break with the 1-to-1 mapping from real to virtual space. Instead, specialized techniques for 3D interaction and haptic retargeting leverage hand redirection, offsetting the virtual hand rendering from the real hand position. To achieve unnoticeable hand redirection, however, the utilization of change blindness phenomena has not been systematically explored. Inspired by recent advances in the domain of redirected walking, we present the first hand redirection technique that makes use of blink-induced visual suppression and corresponding change blindness. We introduce Blink-Suppressed Hand Redirection (BSHR) to study the feasibility and detectability of hand redirection based on blink suppression. Our technique is based on Cheng et al.'s (2017) [9] body warping algorithm and instantaneously shifts the virtual hand when the user's vision is suppressed during a blink. Additionally, it can be configured to continuously increment hand offsets when the user's eyes are opened, limited to an extent below detection thresholds. In a psychophysical experiment, we verify that unnoticeable blink-suppressed hand redirection is possible even in worst -case scenarios, and derive the corresponding conservative detection thresholds (CDTs). Moreover, our results show that the range of unnoticeable redirection can be increased by combining continuous warping and blink-suppressed instantaneous shifts. As an additional contribution, we derive the CDTs for Cheng et al.'s (2017) [9] redirection technique that does not leverage blinks.