Figure 2.

(Color online) (a) Illustration of the nonlinear spring-based contact force. Each surface vertex of the triangular mesh on one VF is connected to every surface vertex on the opposite VF with non-linear springs. The solid line represents activated springs and the dashed line represents inactivated springs. “F” is the spring force and it is further decomposed into “F_n” and “F_t,” which are the normal and tangential components with respect to the local curvature of the VF surface, respectively. (b) Spring force versus distance between two contacting nodes.