Real-time knotting and unknotting

Suturing simulations, of which real-time knotting and unknotting are the most challenge parts, are essential to today's surgical training systems. In this paper, we present a physics-based approach to real-time simulation of deformable linear objects (DLOs) with visual and force feedback. In our suture model, which can represent the mechanical properties of a real thread such as stretching, compressing, bending, and twisting, we simulate not only external forces, but also internal forces including the friction force during knotting and unknotting. We also present how forces propagate along the suture when the user pulls it with one or two hands. We developed a simulator to allow users to grasp and smoothly manipulate a virtual thread, and to tie an arbitrary knot.