Six degree-of-freedom haptic simulation of sharp geometric features using a hybrid sphere-tree model

Subtle force feelings caused by contacts at sharp geometric features are necessary to achieve high-fidelity haptic rendering. It is a challenging problem to achieve six degree-of-freedom (6-DOF) haptic simulation with sharp features for multi-region contacts scenario. We propose a configuration-based optimization method using a hybrid sphere-tree model to compute constraint-based collision response. Based on the variance of dihedral angle between adjacent triangles, an original triangle mesh of the simulated object is segmented into a hybrid sphere-tree model, i.e. a hierarchical sphere-tree for global shape and several linear-lists of spheres for local areas with sharp features. In each local area with sharp features, we first identify those spheres which radius is larger than a pre-defined perceptual threshold. Then these spheres are divided into a linear list of smaller spheres by a splitting method. The experiment results on a sphere-cube interaction and a spline-shaped peg-hole interaction validate that the proposed method can simulate a subtle force direction change when sliding contact occurs across the sharp edges. Non-penetration between the two objects can be maintained for multi-region contacts scenario. The haptic rendering rate is over 1kHz and the interaction is stable.