Haptic Force Shading Parameter Effects on Path Tracing Accuracy

3D haptic drawing and painting require accurate interfaces for surface interaction. This study investigates the potential of varying stiffness and normal interpolation distance to improve the accuracy of surface path tracing performance on faceted meshes rendered with haptic force shading. For single point haptic feedback simulated with a sensable PHANToM arm, a formula for the just noticeable difference (JND) of stiffness was also derived. Higher stiffnesses reduced drawing errors up to a point, with an insignificant fall-off above an intermediate stiffness value of .55N/mm. The normal interpolation distance did not affect errors. Better surface path tracing accuracy was achieved by users who exerted lower forces, revealing the role of shortcomings in the surface contact point calculation method used by the General Haptic Open Software Toolkit (GHOST).