Right Triangular Irregular Networks

We describe a hierarchical data structure for representing a digital terrain (height eld) which contains approximations of the terrain at diierent levels of detail. The approximations are based on triangulations of the underlying two-dimensional space using right-angled triangles. The methods we discuss allow the approximation to precisely represent the surface in certain areas while coarsely approximating the surface in others. Thus, for example, the area close to an observer may be represented with greater detail than areas which lie outside their eld of view. We discuss the application of this hierarchical data structure to the problem of interactive terrain visu-alization. We point out some of the advantages of this method in terms of memory usage and speed.