Occlusion resolution operators for three-dimensional detail-in-context

The information explosion is changing the daily lies of the "wired" population. Increasing numbers of individuals are being empowered to act as their own information brokers, interacting with large and expanding data spaces, for example the World Wide Web. Scientists too are dealing with growing databases of empirical and simulated information. New tools for visualizing these spaces are being developed which incorporate three-dimensional visual representations of information. These three-dimensional representations are believed to leverage the individual's capacity for comprehension and navigation in our three-dimensional world. In practice one is faced with the inherent limitations of 2D presentation and interaction through the traditional two-dimensional desktop computer display.; The spatial limitations of the two-dimensional display (referred to as the "screen real-estate problem") have motivated the development of detail-in-context methods of information presentation and exploration. Much of the work in this field has concentrated on presentation methods for 2D information spaces. While a few techniques have incorporated 3D interaction metaphors, such as surfaces which produce magnification through perspective distortion, fewer still have focused on techniques for interaction with 3D representations of information. Three-dimensional representations of information present specific challenges not found in 2D representations, for example the effect of occlusion on the visibility of elements. Traditional approaches to dealing with occlusion in three-dimensional representations include techniques such as cutting planes, viewer navigation, filtering of information and transparency. While these methods provide clearer visual access to elements of interest it is often at the expense of removing much of the contextual information from a representation.; We present a technique which employs a new approach to some of the challenges in interacting with 3D representations of information. Specifically we resolve occlusion of objects in a 3D scene through a layout adjustment algorithm derived from 2D detail-in-context viewing methods. Our extension beyond traditional 2D approaches to layout adjustment in 3D accounts for the specific challenges of occlusion in 3D representations, where other such extensions do not. In doing so we provide a simple vet powerful tool for providing non-occluded views of objects or regions of interest in a 3D information representation with minimal adjustment of the original structure and without the use of cutting planes, transparency or information filtering. We call these operators Occlusion Reducing Transformations (ORTs).