Direct haptic rendering of isosurface by intermediate representation

With the development of volume visualization methods, we can easily extract meaningful information from volumetric data using interactive graphics and imaging. Haptic interaction of volumetric data adds a new modality to volume visualization that has an advantage in presenting complex attributes of local region. However, the benefits of haptic rendering of volumetric data have only been recognized recently. Most traditional haptic rendering methods are developed to compute realistic interaction force with geometric primitives. Direct volume haptic rendering allows haptic palpation of volumetric data, but lacks of the ability of simulating the contact sensation of stiff embedded implicit surface.In this paper, we propose a direct haptic rendering method for isosurface in volumetric data using a point-based haptic feedback device, without the extraction of the isosurface to geometric representations such as polygons. Our algorithm extends the intermediate representation approach that had been introduced for dealing with complex virtual environment, to haptically render volumetric data. The algorithm uses a virtual plane as an intermediate representation of the implicit isosurface, and computes the point interaction force applied to the haptic interface based on this virtual plane. Using this approach, we are able to gain higher haptic servo rate for volumetric data. It makes maintenance of the stability of the simulation easier, and applicable to noisy data without preprocessing. We have developed our algorithm and tested with synthetic data and medical data, using the PHANToMTM haptic interface.