DobbyEar: Inducing Body Illusion of Ear Deformation with Haptic Retargeting

Research Background and Problem

• Identified Problems or Challenges: Current virtual reality (VR) technologies are widely used to create body illusions to enhance the sense of body ownership over virtual avatars. However, existing methods often rely on mechanical devices or proxies to provide tactile feedback, making it difficult to achieve fine deformation illusions for complex body parts such as ears.
• Significance: Ears are a critical facial feature that significantly impacts the appearance of virtual avatars and the user's immersive experience. Additionally, the fixed shape of ears and their consistent alignment with head-mounted display (HMD) positions make them an ideal target for deformation simulation research. Addressing this issue could unlock new possibilities for virtual avatar design and immersive user experiences.
• Research Motivation and Related Work:
  • Previous studies have induced body ownership through multisensory stimulation (visual and tactile), but these approaches often rely on complex experimental setups or simple one-dimensional changes (e.g., length extension), limiting their applicability to complex shape deformations.
  • Haptic retargeting technology can redirect users' hand movements to reallocate real and virtual tactile locations without requiring synchronized mechanical feedback, showing potential for inducing more complex body illusions.

Solution

• Proposed Method or Solution:
  • This study employs haptic retargeting technology to map the tactile sensation of a user's hand on a virtual ear to the physical location of their real ear, thereby inducing a body illusion of ear deformation and enhancing the sense of body ownership over the virtual avatar.
• Innovations:
  • Introduced an innovative method to induce ear deformation without the need for mechanical devices or synchronized feedback.
  • Combined linear mapping with contact point retargeting to dynamically match the contours of virtual and physical ears, achieving a refined tactile experience.
  • Explored, for the first time, the extent to which haptic retargeting influences users' sense of body ownership.
• Implementation Steps and Key Techniques:
  1. Haptic Mapping: Introduced a mapping algorithm to shift the user's virtual ear contact points to the real ear contact points while adjusting the spatial offset between the physical and virtual hands.
  2. Contour Matching: Linearly mapped the virtual ear contour to the physical ear contour to ensure that the user's fingers always contact the correct physical location while sliding along the ear's shape.
  3. Experimental Design: Conducted user experiments to validate the acceptability of haptic retargeting and its effect on enhancing the sense of body ownership over virtual avatars. Experiments included ear deformations involving angular offsets, size changes, and shape modifications.

Research Outcomes

• Specific Findings:
  • Identified the range of user acceptance for ear haptic retargeting (angular offset range of -10° to 50° or -20° to 40°).
  • Demonstrated that haptic retargeting significantly enhances the sense of body ownership over virtual ears, regardless of whether the ear's size or shape differs from the real ear.
  • Found that haptic retargeting could still enhance the sense of ownership for non-human avatars (e.g., dog ears).
• Advantages Over Existing Solutions:
  • No Need for Specialized Mechanical Devices: Significantly reduces system complexity and experimental costs.
  • Wide Applicability: Supports not only linear deformations but also complex shape contour deformations.
  • Low User Burden: Requires only simple calibration, eliminating the need for 3D body scanning, making it easier to adapt and deploy compared to existing studies.
• Experimental or Evaluation Results:
  • Study 1: Users widely accepted angular offsets of 10° to 50° (without head movement) and -20° to 40° (with head movement) for virtual ears.
  • Study 2: Haptic retargeting significantly enhanced the sense of body ownership over virtual ears, regardless of whether the ears were stretched or proportionally resized, with the effect being most pronounced for ears of original size.
  • Study 3: Even when ears were deformed into non-human forms (e.g., cat ears or dog ears), haptic retargeting significantly improved users' sense of ownership over the virtual ears.
• Limitations and Future Directions:
  • Limitations:
    1. The current method only supports contour touch with fixed start and end points, not allowing users to freely choose contact points.
    2. User head movements may dynamically alter the haptic retargeting offset, affecting the consistency of the experience.
  • Future Directions:
    1. Extend the method to other body parts (e.g., chin, forearm) to induce more complex body illusions.
    2. Optimize the algorithm to support dynamic target positions and free-touch interactions.
    3. Explore the effects of haptic retargeting and its impact on the sense of ownership in more complex ear scenarios (e.g., wearing earrings).

Through this study, the authors demonstrate the potential of haptic retargeting in enhancing the sense of body ownership over virtual bodies and expanding the design capabilities of virtual appearances, laying the foundation for broader applications of virtual reality technology in human-computer interaction.