Haptizing a Surface Height Change with Varying Stiffness Based on Force Constancy: Effect of Surface Normal Render

This work has been motivated by our prior efforts for perceptualizing the scientific data sets of surface topography and stiffness distribution measured with a scanning probe microscope. Previously, we showed that the surface topography information with varying stiffness rendered with the conventional penalty-based method can be distorted (Choi et al., 2005), and developed a topography compensation algorithm based on the theory of force constancy in order to resolve the problem (Cheon and Choi, 2006). The theory of force constancy states that the user maintains an invariant contact force level when s/he strokes a surface to perceive its topography. As a follow-up study, this paper investigates the benefits of including surface normal rendering in the haptization of a surface height change with varying stiffness, through a simulation and a psychophysical experiment. Adequate surface normal rendering creates lateral force cues when a haptic interface tool crosses a height change interval. The results indicated that surface normal rendering facilitates correct perception of surface height changes, in particular, for very low height changes