Understanding Usability of VR Pointing Methods with a Handheld-style HMD for Onsite Exhibitions

Research Background and Issues

What problems or challenges did the authors identify?

• In on-site exhibitions, handheld-style head-mounted displays (HMDs) offer a more convenient virtual reality (VR) content experience but lack standard practices for basic interactions, particularly pointing methods.
• When using handheld HMDs, users can only operate with one hand while continuously holding up the device for interaction, which may increase fatigue and negatively impact interaction quality.
• Current pointing methods (controllers and gestures), while effective, have usability issues, such as being unintuitive for beginners or cumbersome to operate.

Why is this issue important?

• In public VR exhibitions, many attendees are first-time VR users and unfamiliar with 3D interactions. Interaction difficulties can limit the breadth and depth of user experience.
• Without properly optimized pointing methods, the experience may be inefficient, error-prone, and potentially alienate potential audiences, reducing the exhibition's appeal.
• Optimizing interaction methods for handheld HMDs can promote their application in public settings, thereby facilitating broader acceptance of VR technology.

Research Motivation and Related Work

• The authors observed that the industry and research community lack systematic studies on interactions with handheld HMDs, and existing pointing methods remain at the stage of adapting current devices or using existing techniques.
• Insights from prior research indicate that practices involving handheld HMDs are still exploring optimal interaction methods, particularly pointing operations, which remain uncertain.

Solution

What methods or solutions did the authors propose?

• The authors designed and evaluated seven different pointing methods, combining targeting and selection techniques:
  1. Controller+Controller Button (controller ray combined with controller button selection)
  2. Hand+Gesture (hand ray combined with gesture selection)
  3. Hand+Dwell (hand ray combined with dwell time selection)
  4. Hand+Trigger Button (hand ray combined with device handle button selection)
  5. Head+Gesture (head ray combined with gesture selection)
  6. Head+Dwell (head ray combined with dwell time selection)
  7. Head+Trigger Button (head ray combined with device handle button selection)

What are the innovative aspects of this solution?

• Combining existing practices (e.g., controller and gesture interaction methods) with new input techniques (e.g., dwell time, trigger buttons) to form a systematic comparison.
• Embedding trigger buttons into handle designs through DIY methods to accommodate practitioners' device assembly needs.
• Comparing multiple pointing methods from the perspective of user experience, including performance, efficiency, and usability, to guide interaction design suitable for on-site exhibitions.

What are the implementation steps and key technologies used?

1. Design Phase:
   • Conduct interviews and literature reviews to select mainstream targeting and selection techniques.
   • Create handheld HMD devices and use 3D-printed connectors to transform controllers into device handles.
2. Method Implementation and Testing:
   • Implement seven pointing methods in the Unity 2022 development environment.
   • Set up experimental tasks: Fitts’ Law tasks based on ISO 9241-9 to simulate target selection scenarios in actual exhibitions.
3. User Study:
   • Recruit 28 participants (mostly VR beginners) to operate and evaluate the seven pointing methods.
   • Collect data metrics (movement time, error rate, throughput) and subjective evaluations (SUS, Raw-TLX).

Research Outcomes

What specific results were achieved?

• The controller ray combined with button selection method (Controller+Controller Button) performed best in speed and throughput but had a higher error rate compared to dwell time methods.
• The dwell time combined with head ray selection method (Head+Dwell) had the lowest error rate (0%) and performed best in workload and user confidence.
• The gesture combined with hand ray method (Hand+Gesture) performed the worst and is not recommended for on-site exhibitions.

What advantages does it have compared to existing solutions?

• The dwell time method significantly reduced error rates and improved user confidence, making it particularly suitable for users with no prior VR experience.
• The head ray combined with trigger button selection method (Head+Trigger Button) offered high efficiency and user preference, reducing the complexity of device distribution compared to traditional controller operations.

What were the experimental or evaluation results?

• Performance Metrics:
  • The Controller method had the fastest movement time (0.86s) and highest throughput (3.19 bit/s).
  • The dwell time methods performed best in error rates (Head+Dwell: 0%, Hand+Dwell: 0.89%).
• Subjective Evaluations:
  • SUS scores indicated that the Head+Dwell method had the highest user satisfaction (79.55).
  • Raw-TLX scores showed that the Head+Dwell method had the lowest workload (28.27).

Limitations and Future Directions

• Task Design Limitations: The study focused on simple 2D selection tasks, failing to reflect the complexity of 3D interactions.
• Device Form Limitations: The research was limited to single-handle handheld HMDs, and devices with different structures may require reevaluation of interaction methods.
• Incomplete Coverage of Interaction Technologies: Techniques such as eye tracking and voice input were not included, which could offer more natural interaction methods.

Future Directions:

1. Expanding Interaction Technology Scope: Include eye tracking and voice recognition.
2. Studying Complex Task Scenarios: Introduce more complex 3D tasks and visual search tasks.
3. Real-world Application Testing: Conduct "field studies" in actual exhibition environments to validate the effectiveness of interaction methods.

Through this research, the authors proposed optimized interaction methods for handheld HMDs, recommending dwell time methods as the preferred choice for on-site exhibitions. The findings lay the foundation for the widespread application of handheld HMDs and provide practical guidance for improving exhibition experiences.