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



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 triangu-
lation 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.