Human Head Stiffness Rendering

Human head stiffness rendering is important in haptic interactive applications, because it defines a realistic physical interaction between human operator(s) and a human avatar created in a virtual environment. In this paper, we propose a hybrid method for rendering the appropriate stiffness property on a human head polygon mesh that combines popular haptic rendering approaches: study the sophisticated deformation behavior of a deformable object and then interpret and render this behavior as the resulting stiffness property on the individual's head mesh. The stiffness property is estimated from a registered and shape-adapted skull template mesh as a reference and modeled from the deformation behavior of soft tissue in a finite-element method (FEM) framework. Our method consists of different procedures, including facial landmark detection, model registration using the iterative closest point technique, adaptive shape modification processed with a modified weighted free-form deformation, and FEM simulation. After the stiffness property is rendered on a head polygon mesh, we perform a user study by inviting participants to experience the haptic feedback rendered from our results. According to the participants' feedback, the stiffness property of the head polygon mesh is properly rendered, because it satisfies their expectations.