A simple, fast, and approximate voxel-based approach to 6-DOF haptic rendering is presented. It can reliably sustain a 1000 Hz haptic refresh rate without resorting to asynchronous physics and haptic rendering loops. It enables the manipulation of a modestly complex rigid object within an arbitrarily complex environment of static rigid objects. It renders a short-range force field surrounding the static objects, which repels the manipulated object and strives to maintain a voxel-scale minimum separation distance that is known to preclude exact surface interpenetration. Force discontinuities arising from the use of a simple penalty force model are mitigated by a dynamic simulation based on virtual coupling. A generalization of octree improves voxel memory efficiency. In a preliminary implementation, a commercially available 6-DOF haptic prototype device is driven at a constant 1000 Hz haptic refresh rate from one dedicated haptic processor, with a separate processor for graphics. This system yields stable and convincing force feedback for a wide range of user controlled motion inside a large, complex virtual environment, with very few surface interpenetration events. This level of performance appears suited to applications such as certain maintenance and assembly task simulations that can tolerate voxel-scale minimum separation distances.

A high performance six degree-of-freedom magnetic levitation haptic interface device has been integrated with a physically-based dynamic rigid-body simulation to enable realistic user interaction in real time with a 3-D dynamic virtual environment. The user grasps the levitated handle of the device to manipulate a virtual tool in the simulated environment and feels its force and motion response as it contacts and interacts with other objects in the simulation. The physical simulation and the magnetic levitation controller execute independently on separate processors. The position and orientation of the virtual tool in the simulation and the levitated handle of the maglev device are exchanged at each update of the simulation. The position and orientation data from each system act as impedance control setpoints for the other, with position error and velocity feedback on each system acting as virtual coupling between the two systems. The setpoints from the simulation are interpolated by the controller at the faster device control rate so that the user feels smooth sliding contacts without chattering due to the slower updates of the simulation. The simple feedback coupling between the two systems enables the overall stiffness and stability of the combined system to be tuned easily and provides realistic haptic user interaction. Sample task simulation environments have been programmed to demonstrate the effectiveness of the haptic interaction system.