Shadows of Reality: Enhancing Bystander Awareness of Mixed Reality Interfaces

Spaces shared by Mixed Reality (MR) users and bystanders (non-MR users) pose unique challenges because bystanders cannot see the virtual interfaces that the MR user is interacting with. As a result, they may unknowingly occlude these interfaces, leading to physical-virtual conflicts that disrupt the MR user’s experience. To address this issue, we explore how projecting shadows of virtual interfaces onto the floor can enhance bystander awareness. We conducted a user study (N = 20) in which a bystander performed an independent task in the same space as an MR user. The bystander experienced one of three visualization conditions - none (no projection), dynamic (shadows appear only upon collision), and always-on (shadows of all interfaces are continuously visible). Our findings show that always-on significantly mitigated physical-virtual conflicts and was most preferred by participants. In contrast, the dynamic condition was found to be distracting, while none required extra communication and led to more interference. Our results highlight the value of persistent, easily perceived cues for bridging the perceptual divide between MR users and bystanders in shared physical spaces, ultimately promoting more seamless integration of MR systems into everyday environments.

@inproceedings {Khan2025Shadows, 
 author = {Khan, Talha and Zimmerman, Abigail and Andrews, Edward and Lindlbauer, David and Biehl, Jacob}, 
 title = {Shadows of Reality: Enhancing Bystander Awareness of Mixed Reality Interfaces}, 
 year = {2025}, 
 publisher = {Association for Computing Machinery}, 
 address = {New York, NY, USA}, 
 url = {https://doi.org/10.1145/3694907.3765920}, 
 keywords = {Mixed reality, Visualizations, Shared spaces, Bystander awareness}, 
 series = {SUI '25} 
 }