RESUMEN
The ability to manipulate and physically feel virtual objects without any real object being present and without equipping the user has been a long-standing goal in virtual reality (VR). Emerging ultrasound mid-air haptics (UMH) technology could potentially address this challenge, as it enables remote tactile stimulation of unequipped users. However, to date, UMH has received limited attention in the field of haptic exploration and manipulation in virtual environments. Existing work has primarily focused on interactions requiring a single hand and thus the delivery of unimanual haptic feedback. Despite being fundamental to a large part of haptic interactions with our environments, bimanual tasks have rarely been studied in the field of UMH interaction in VR. In this paper, we propose the use of non-coplanar mid-air haptic devices for providing simultaneous tactile feedback to both hands during bimanual VR manipulation. We discuss coupling schemes and haptic rendering algorithms for providing bimanual haptic feedback in bimanual interactions with virtual environments. We then present two human participant studies, assessing the benefits of bimanual ultrasound haptic feedback in a two-handed grasping and holding task and in a shape exploration task. Results suggest that the use of multiple non-coplanar UMH devices could be an interesting approach for enriching unencumbered haptic manipulation in virtual environments.
RESUMEN
Rich, informative and realistic haptic feedback is key to enhancing Virtual Reality (VR) manipulation. Tangible objects provide convincing grasping and manipulation interactions with haptic feedback of e.g., shape, mass and texture properties. But these properties are static, and cannot respond to interactions in the virtual environment. On the other hand, vibrotactile feedback provides the opportunity for delivering dynamic cues rendering many different contact properties, such as impacts, object vibrations or textures. Handheld objects or controllers in VR are usually restricted to vibrating in a monolithic fashion. In this paper, we investigate how spatialiazing vibrotactile cues within handheld tangibles could enable a wider range of sensations and interactions. We conduct a set of perception studies, investigating the extent to which spatialization of vibrotactile feedback within tangible objects is possible as well as the benefits of proposed rendering schemes leveraging multiple actuators in VR. Results show that vibrotactile cues from localized actuators can be discriminated and are beneficial for certain rendering schemes.
RESUMEN
We propose to study the combination of acoustically transparent tangible objects (ATTs) and ultrasound mid-air haptic (UMH) feedback to support haptic interactions with digital content. Both these haptic feedback methods have the advantage of leaving users unencumbered, and present uniquely complementary strengths and weaknesses. In this article, we provide an overview of the design space for haptic interactions covered by this combination, as well as requirements for their technical implementation. Indeed, when imagining the concurrent manipulation of physical objects and delivery of mid-air haptic stimuli, reflection and absorption of sound by the tangibles may impede delivery of the UMH stimuli. To demonstrate the viability of our approach, we study the combination of single ATT surfaces, i.e. the basic building blocks for any tangible object, and UMH stimuli. We investigate attenuation of a focal point focused through various plates of acoustically transparent materials, and run three human subject experiments investigating the impact of acoustically transparent materials on detection thresholds, discrimination of motion, and localization of ultrasound haptic stimuli. Results show that tangible surfaces which do not significantly attenuate ultrasound can be fabricated with relative ease. The perception studies confirm that ATT surfaces do not impede perception of UMH stimulus properties, and thus that both may viably be combined in haptics applications.