Force and contact location shading methods for use within two- and three-dimensional polygonal environments

Current state-of-the-art haptic interfaces only provide kinesthetic (force) feedback. Providing tactile feedback in concert with kinesthetic information can dramatically improve one's ability to dexterously interact with and explore virtual environments. In this research, tactile feedback was provided by a device, called a contact location display (CLD), that is capable of rendering (displaying) the center of contact to a user. The chief goal of this work is to develop algorithms that allow the CLD to be used with polygonal geometric models, which are commonly used to model haptic virtual environments. However, the use of polygonal models with the contact location display introduces an issue - the addition of tactile feedback enhances the saliency of the vertices and edges of polygonally represented (smooth) objects. That is, one can be distracted by the tactile sensations rendered when passing over the edges of the polygonal model. Two haptic "shading" algorithms were developed to address this issue and each provides smooth tactile and kinesthetic feedback. The first shading algorithm was developed for a two-dimensional environment for a proof of concept and because the current CLD device is only capable of rendering contact positions lengthwise along the finger. Performance thresholds that specify the required number of polygons to render a smooth curve were evaluated in an experiment. It was found that the addition of contact location feedback significantly increases user sensitivity to small facets and features and the developed algorithm proved to create smoother interactions than prior shading techniques. The second shading algorithm was developed to expand the first algorithm to three dimensions. An object recognition task was performed as both a demonstration of the 3D haptic shading algorithm and to provide further insight into the current CLD's capability to facilitate exploration and shape recognition. The study found the shading algorithm increased the amount of time users were able to stay in contact with the objects; however, these experiments also suggest that the current CLD device needs further mechanical revisions before it can provide effective haptic interactions in 3D environments. Both of the developed shading algorithms create smooth haptic surfaces with accurate geometric representations and successfully extend the use of the contact location display to polygonal models. The presented results provide guidelines for future work and revision of the CLD device.