No More Head-Turning: Exploring Passthrough Techniques for Addressing Rear Interruptions from the Front in VR

TL;DR

This paper addresses the challenge of rear-origin interruptions in VR and the burden of head turning during Passthrough. It first establishes that interruption direction strongly influences Passthrough usage, then proposes three front-facing rear-awareness techniques: Full Rear Passthrough + Pause (FRPP), Rear Passthrough Window (RPW), and Rear Passthrough AR (RPAR). Through a two-study program, it demonstrates that FRPP and RPAR reduce physical and temporal demands, lessen motion sickness, and improve usability and presence, with FRPP often preferred due to its pausing capability. The findings offer design guidance for VR systems to better support rear interruptions without compromising immersion, suggesting mirrored rear views and option choices between pausing or continuous view as practical strategies.

Abstract

Virtual reality (VR) users often encounter interruptions, posing challenges to maintaining real-world awareness during immersive experiences. The Passthrough feature in VR headsets allows users to view their physical surroundings without removing the headset. However, when interruptions come from the rear, users need to turn their heads to see the real world, which can lead to negative experiences in VR. Study 1, conducted through semi-structured interviews involving 13 participants, found that users are less likely to use Passthrough for rear interruptions due to large head-turning movements, which cause inconvenience, increase the risk of motion sickness, and reduce the experience. Building on these findings, we introduced three Passthrough techniques in Study 2 for displaying the rear view in front of the user: Full Rear Passthrough + Pause (FRPP), Rear Passthrough Window (RPW), and Rear Passthrough AR (RPAR). Compared to the Baseline method that requires head-turning, all three systems reduced physical and temporal demands, alleviated disorientation caused by motion sickness, and provided a better user experience for managing rear interruptions. Among these, FRPP and RPAR were the most preferred. These findings provide valuable insights for future VR design, emphasizing the need for solutions that effectively manage rear interruptions while maintaining user comfort and experience.

Figures (5)

• Figure 1: A participant using the controllers to slice the incoming fruits in the game.
• Figure 2: The four types of interruptions in the experiment: (a) Someone Entering the Room, (b) an Object Falling, (c) Someone Laughing, and (d) Someone Asking about an Object.
• Figure 3: System usability scores for each condition, showing significant differences in Disruptive, Frustrating, Urgent, Informative, Communicative, and Too Aware of Reality. Error bars indicate 95% confidence intervals. *, **, and *** indicate statistical significance at the $p < 0.05, p < 0.01,$ and $p < 0.001$ levels, respectively.
• Figure 4: (a) NASA-TLX scores for each condition, showing significant differences in Mental Demand, Physical Demand, Temporal Demand, and Effort. (b) Presence experience scores for each condition, showing significant differences in Sense of Being There and Involvement. (c) SSQ scores for each condition, showing significant differences in Total Score and Disorientation. Error bars indicate 95% confidence intervals. *, **, and *** indicate statistical significance at the $p < 0.05, p < 0.01,$ and $p < 0.001$ levels, respectively.
• Figure 5: Participant preference ranking across the four conditions.