Soft-Touch Haptics Modeling of Dynamic Surfaces

Introduction

Haptics studies the modality of touch and associated sensory feedback. In contrast to the other sensory channels such as visual and auditory, haptic interaction is the only technique that can provide touch-enabled dynamic & interactive 3D display to users. It is an active research field to improve the immersive reality of virtual environments (Chen & Sun, 2006), especially in simulations where it is crucial for the operators to touch, grasp and manipulate the virtual soft objects realistically as in the physical world. Soft-touch haptics modeling is the core component in feeling and manipulating dynamic objects within the virtual environments. Augmenting soft-touch realism in deformable objects provides new touch characteristic in addition with graphical display, and covers a wide range of applications (Aamisepp & Nilsson, 2003) such as geometric modeling, computer animation, and on-line game development.

We present soft-touch haptics modeling and rendering mainly in three themes: multiple force-reflecting dynamics in Loop subdivision surfaces; soft-touch physical freeform deformations; force constraints in interactive design. Loop subdivision is designed to generalize the recurrence relations for the three-directional quartic box splines to triangular meshes of arbitrary topology (Loop, 1987). Because triangular meshes arise in many applications, Loop subdivision becomes one of the most popular subdivision schemes. Subdivision surfaces are motivated to uniformly model any complex surfaces of arbitrary topology. Dynamic subdivision surfaces allow the shape editing of limit surfaces by applying forces interactively on the control meshes, and thus enable the creation of intuitive interface for geometric modeling such as modeling with clay dough. We incorporate the 6-DOF haptic interface in the dynamic modeling of Loop surfaces, where the dynamic parameters are computed easily without subdividing the control mesh recursively. During the haptic interactions, the contact point is traced and reflected to the rendering of updated graphics and haptics. Based on the multi-resolution surfacing representation, our approach permits the users to touch the virtual objects at the varying detailed surfacing levels, and manipulate the dynamics by applying the intuitive forces through the real-time haptic interface.