Exploration of Radar-based Obstacle Visualizations to Support Safety and Presence in Camera-Free Outdoor VR

2026-02-01

AI Summary

This work addresses the challenge of balancing user safety, immersion, and privacy in outdoor virtual reality, where existing camera-based obstacle-awareness systems pose significant privacy risks. To overcome this limitation, we propose WaveWalkerClone—the first camera-free perception system leveraging millimeter-wave radar for real-time environmental sensing. Through a user study, we systematically evaluate three visualization strategies—diegetic alien avatars, non-diegetic human avatars, and abstract point clouds—examining their trade-offs in safety support, cognitive load, and user experience. Results demonstrate that all three approaches effectively enable situational awareness and obstacle avoidance, yet they differ significantly in perceived user effort, frustration, and subjective preference. Our findings validate a novel paradigm for immersive VR design that prioritizes both personalization and privacy preservation without compromising safety or presence.

Technology Category

• Humans and AI: Game Design — Virtual Humans, NPCs and Autonomous Characters
• Computer Vision: Motion & Tracking
• Intelligent Robots: Multimodal Perception & Sensor Fusion

Application Category

• User Modeling, Personalization and Recommendation: User privacy protection in personalized systems
• Responsible Web: Human-perceived consequences of algorithmic deployment on the web
• Security and Privacy: Large-scale security measurements

Abstract

Outdoor virtual reality (VR) places users in dynamic physical environments where they must remain aware of real-world obstacles, including static structures and moving bystanders, while immersed in a virtual scene. This dual demand introduces challenges for both user safety and presence. Millimeter-wave (mmWave) radar offers a privacy-preserving alternative to camera-based sensing by detecting obstacles without capturing identifiable visual imagery, yet effective methods for communicating its sparse spatial information to users remain underexplored. In this work, we developed and validated WaveWalkerClone, a reproduction of the WaveWalker system, to establish reliable radar- and GPS-IMU-based sensing under varied outdoor lighting conditions. Building on this feasibility validation, we conducted a user study (n=18) comparing three visualization techniques for radar-detected obstacles : (1) diegetic alien avatars that visually embed obstacles within the virtual narrative, (2) non-diegetic human avatars represented obstacles as humans inconsistent with the virtual narrative, and (3) abstract point clouds centered around the obstacles conveying spatial data without anthropomorphic or narrative associations. Our results show that all three approaches supported user safety and situational awareness, but yielded distinct trade-offs in perceived effort, frustration, and user preference. Qualitative feedback further revealed divergent user responses across conditions, highlighting the limitations of a one-size-fits-all approach. We conclude with design considerations for obstacle visualization in outdoor VR systems that seek to balance immersion, safety, and bystander privacy.

Problem

• outdoor VR
• obstacle visualization
• mmWave radar
• user safety
• presence

Innovation

• mmWave radar
• outdoor VR
• obstacle visualization
• privacy-preserving sensing
• diegetic representation