Real-Time Generation of Continuous Levels of Detail for Height Fields.pdf

Real-Time Generation of Continuous Levels of Detail for Height Fields Stefan Ro?ttger (snroettg@immd9.informatik.uni-erlangen.de) Wolfgang Heidrich, Philipp Slusallek, Hans-Peter Seidel Graphische Datenverarbeitung (IMMD9) Universita?t Erlangen-Nu?rnberg ABSTRACT Height fields play an important role in the fast growing domain of Geographic Information Systems (GIS). For exploring different kinds of geographic-based data sets on screen it is necessary to display height fields at interactive frame rates. Because of the inherent geometric complexity, this goal is often unachievable even with new generations of powerful graphics computers, unless the original height field data is approximated in order to reduce the number of geometric primitives that need to be rendered without compromising visual quality. So far most algorithms have focused on global reduction or multi-resolution techniques, which reduce resolution on the basis of surface roughness. A recent new approach called Continuous Levels of Detail [LKR 96] introduced a hierarchical quadtree technique. In order to reduce the projected pixel error, the height field is dynamically triangulated in a bottom up fashion according to the distance to the point of view. Since resolution is allowed to change smoothly, the result is a much better image quality. However, this algorithm still has a major disadvantage. With the viewpoint moving, the triangulation is continuously changing, resulting in a phenomenon called vertex popping. As the observer approaches an area with detail information, this detail will suddenly appear at a certain distance. To eliminate these artifacts we introduce a new, rapid geomorphing algorithm, which operates top down on a quadtree data structure. 1 Introduction A fast growing domain in computer graphics are the so called Geographic Information Systems (GIS). They allow to explore large geographic data sets interac- tively on screen, which involves displaying height fields in real-time. Typi