Virtual grasp release method and evaluation

Abstract

We address a “sticking object” problem for the release of whole-hand virtual grasps. The problem occurs when grasping techniques require fingers to be moved outside an object's boundaries after a user's (real) fingers interpenetrate virtual objects due to a lack of physical motion constraints. This may be especially distracting for grasp techniques that introduce mismatches between tracked and visual hand configurations to visually prevent interpenetration. Our method includes heuristic analysis of finger motion and a transient incremental motion metaphor to manage a virtual hand during grasp release. We integrate the method into a spring model for whole-hand virtual grasping to maintain the physically-based pickup and manipulation behavior of such models. We show that the new spring model improves release speed and accuracy based on pick-and-drop, targeted ball-drop, and cube-alignment experiments. In contrast to a standard spring-based grasping method, measured release quality does not depend notably on object size. Users subjectively prefer the new approach and it can be tuned to avoid potential side effects such as increased drops or visual distractions. We further investigated a convergence speed parameter to find the subjectively good range and to better understand tradeoffs in subjective artifacts on the continuum between pure incremental motion and rubber-band-like convergence behavior.