title: Visuohaptic discrimination of 3D gross shape.
abstract: Human sensitivity to 3D gross shape changes was measured for the visual and haptic sensory channels. Three volume-invariant affine transformations were defined: compressing, shearing and stretching. Participants discriminated a reference 3D object (cube or sphere) from its deformed  shape under three experimental conditions: visual only (on a computer monitor), haptic only (through a point-contact force-feedback device) and visuohaptic simulations. The results indicate that vision is more sensitive to gross shape changes than point-based touch, and that vision dominated  in the visuohaptic condition. In the haptic alone condition, thresholds were higher for shearing and stretching than for compressing. Thresholds were otherwise similar for the three transformations in the vision only or visuohaptic conditions. These trends were similar for the two shapes tested.  A second experiment, conducted under similar conditions but preventing participants from manipulating object orientations, verified that the main conclusion of our research still holds when visual inspection can rely only on a single perspective view of the object. Our earlier studies on 3D  visuohaptic watermarking showed that the haptic channel is more sensitive to surface texture and roughness changes than vision. The thresholds from the present and our earlier studies can potentially be used as the upper limits for selecting watermark strengths in order to ensure watermark  imperceptibility in a 3D visuohaptic watermarking system.
authors.affiliation: Haptic Interface Research Lab, School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN, USA. samuelkim91@gmail.com
authors.forename: Kwangtaek
authors.initials: K
authors.lastname: Kim
authors.forename: Mauro
authors.initials: M
authors.lastname: Barni
authors.forename: Domenico
authors.initials: D
authors.lastname: Prattichizzo
authors.forename: Hong Z
authors.initials: HZ
authors.lastname: Tan
mesh_terms: D000328:Adult; D005260:Female; D005556:Form Perception / Q000502:physiology*; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D010364:Pattern Recognition, Visual / Q000502:physiology*; D011601:Psychophysics; D012684:Sensory Thresholds; D055815:Young Adult