Radi-Eye: Hands-free Radial Interfaces for 3D Interaction using Gaze-activated Head-crossing

Title of the Paper

Radi-Eye: Hands-Free Radial Interfaces for 3D Interaction using Gaze-Activated Head-Crossing

Paper Information

• Research Area: Human-Computer Interaction, Hands-Free Interfaces in Augmented Reality and Virtual Reality
• Keywords: Eye tracking, Gaze interaction, Eye-Head Coordination, Radial Interface, Virtual Reality, Augmented Reality

Research Background and Problem

• Identified Issues or Challenges: Traditional hands-free interaction methods based on eye and head movements suffer from limited expressiveness and insufficient control capabilities, while often encountering unintended inputs (e.g., the Midas Touch problem). Existing solutions typically mitigate these issues through delayed confirmation or additional selection matching techniques, but they fail to fully leverage the natural coordination between the eyes and head to improve interaction efficiency and accuracy.
• Significance: Hands-free interaction in augmented and virtual reality is increasingly applied in head-mounted displays (HMDs). Addressing these issues is crucial for scenarios where hands are unavailable, space is constrained, or operations are fatiguing.
• Motivation and Related Work: This research is inspired by prior studies on the coordination between the eyes and head, combined with radial menu interface design and crossing selection techniques. It explores how natural eye-head interaction can enhance the expressiveness of hands-free interaction.

Solution

• Proposed Solution: Radi-Eye is a pop-up radial interface design based on the Look & Cross technique. Users make selections through gaze preselection and head-crossing activation. The interface integrates both discrete and continuous interaction components while supporting large-scale functionality.
• Innovations:
  1. An interaction method leveraging the natural misalignment between the eyes and head to avoid unintended inputs.
  2. Integration of the Look & Cross technique to enable sequential selection and smooth eye-head interaction.
  3. Introduction of hierarchical nested interactions and pop-up radial menus, scalable to complex multi-parameter command combinations.
• Implementation Steps and Techniques:
  1. Create a pop-up radial menu centered on the user's head position, accessible in any direction of eye and head movement.
  2. Use the Look & Cross technique, where components are activated by gaze and selections are triggered by head-crossing boundaries.
  3. Provide diverse interaction components (e.g., sliders, toggle buttons) supporting nesting, replacement, and command combinations.
  4. Develop three AR and VR applications to validate the performance and design principles of Radi-Eye, including a media player, smart home control, and city-building simulator.

Research Outcomes

• Specific Results:
  1. Developed a hands-free interaction system combining radial interfaces with eye-head movements, applicable in AR and VR environments.
  2. User studies demonstrated that the Radi-Eye interface offers fast and accurate selection capabilities, suitable for complex multi-parameter interaction scenarios.
  3. Through testing Look & Cross techniques and radial interface parameters, the study identified and optimized the effects of ring size and component arrangement on user performance.
• Advantages:
  1. Supports natural and smooth eye-head interaction, avoiding unintended input issues.
  2. Compatible with multi-target selection, continuous input, and large-scale functionality control.
  3. Provides an easily extensible interaction design space, adaptable to various display devices and scenarios.
• Experimental or Evaluation Results:
  1. Users completed tasks with a 1.7% error rate and an average selection time of less than 2 seconds.
  2. Ring size significantly impacted selection accuracy, head movement range, and visual search time, with a medium ring size (35°) recommended.
  3. Subjective user evaluations described the Radi-Eye interface as "natural" and "easy to use," with eye-head coordination reducing error rates.
• Limitations and Future Directions:
  1. The Eye&Head technology primarily focuses on discrete selection; further research is needed to improve precision in continuous component interactions (e.g., sliders).
  2. It can be extended to other interaction modes, such as combining hand or voice input to replace head interaction.
  3. Future work could develop more compact components or adjust component functionalities to accommodate cross-boundary interactions in different directions.

Conclusion

Radi-Eye successfully implements a novel hands-free interaction system combining radial interfaces with eye-head interaction, pioneering a design space based on natural eye-head misalignment interaction. It provides new design principles and practical references for hands-free interfaces in augmented and virtual reality.