How Different Is the Perception of Vibrotactile Texture Roughness in Augmented versus Virtual Reality?

Wearable haptic devices can modify the haptic perception of an object touched directly by the finger in a portable and unobtrusive way.In this paper, we investigate whether such wearable haptic augmentations are perceived differently in Augmented Reality (AR) vs. Virtual Reality (VR) and when touching with a virtual hand instead of one's own hand.We first designed a system for real-time rendering of vibrotactile virtual textures without constraints on hand movements, integrated with an immersive visual AR/VR headset.We then conducted a psychophysical study with 20 participants to evaluate the haptic perception of virtual roughness textures on a real surface touched directly with the finger (1) without visual augmentation, (2) with a realistic virtual hand rendered in AR, and (3) with the same virtual hand in VR.On average, participants overestimated the roughness of haptic textures when touching with their real hand alone and underestimated it when touching with a virtual hand in AR, with VR in between.Exploration behaviour was also slower in VR than with real hand alone, although subjective evaluation of the texture was not affected.We discuss how the perceived visual delay of the virtual hand may produce this effect.