Modelli digitali tridimensionali: realtà virtuale e paesaggio

Digital three-dimensional representation of the world had an impressing evolution and start to show a pervasive distribution. A technology which few years ago was common just in research labs is now becoming a common and cheap resource, with both the advent of digital navigation systems entering in our cars or the digital globes our kids are now playing with. The paper presents a brief overview of the methodologies developed for the digital representation of terrains and urban scenes. We present the main technologies for the construction of digital terrain models. Then, we introduce the issues raised by the need of presenting visually those datasets, in the framework of the interactive visualization systems deployed on standard PC-based platforms. The common rendering optimizations, namely geometry culling and data simplification, are introduced; the methodologies and data structures for multiresolution encoding and rendering of terrain data are presented with some more detail. Finally, we present the case of urban models construction and rendering, a topic that is less consolidated than digital terrains but shows an enormous interest in applications.