This paper describes the analysis, optimized redesign and evaluation of a high fidelity vibrotactile interface integrated in a rigid surface. The main application of the embodiment described here is vibrotactile display of virtual ground surface material properties for immersive environments, although the design principles are general. The device consists of a light, composite plate mounted on an elastic suspension, with integrated force sensors. It is actuated by a single voice coil motor. The structural dynamics of the device were optimized, within constraints imposed by the requirements of user interaction, and corrected via digital inverse filtering, in order to enable accurate simulation of virtual ground materials. Measurements of the resulting display demonstrate that it is capable of accurately reproducing forces of more than 40 N across a usable frequency band from 50 Hz to 750 Hz.

When an occluding object, such as a person, stands between a projector and a display surface, a shadow results. We can compensate by positioning multiple projectors so they produce identical and overlapping images and by using a system to locate shadows. Existing systems work by detecting either the shadows or the occluders. Shadow detection methods cannot remove shadows before they appear and are sensitive to video projection, while current occluder detection methods require near infrared cameras and illumination. Instead, we propose using a camera-based object tracker to locate the occluder and an algorithm to model the shadows. The algorithm can adapt to other tracking technologies as well. Despite imprecision in the calibration and tracking process, we found that our system performs effective shadow removal with sufficiently low processing delay for interactive applications with video projection.