Hierarchical simplification of city models to maintain urban legibility

Remco Chang, Thomas Butkiewicz, Caroline Ziemkiewicz, Zachary Wartell, Nancy Pollard, William Ribarsky
2006 ACM SIGGRAPH 2006 Sketches on - SIGGRAPH '06  
Figure 1 : Left to right: (a) Original models (285,039 polygons); (b) Simplified models using our algorithm (131,409 polygons); (c) Models from (b) that have been simplified are shown in yellow; (d) Here we show view-dependent simplification of (b) from a top-down view. Notice that simplified models closer to the eye point have more detailed geometry, while the models farther away have less. Abstract Mesh simplification and discrete levels of detail (LOD) are wellstudied areas of research in
more » ... puter graphics. However, until recently, most of the developed algorithms have focused on simplification and viewing of a single object with a large number of polygons. When these algorithms are used on a large collection of simple models, many objects may be completely erased, leading to results that are misleading to the viewer. In this paper, we present a novel approach to simplifying city-sized collections of 2.5D buildings based on the principles of "urban legibility" as defined by architects and city planners. Our main contributions include a clustering algorithm tailored towards forming logical groups while respecting roads, a polyline simplification algorithm that maintains boundary facades, and a LOD process that preserves landmarks and skylines. The advantage of our approach is that the legibility and understandability of a complex urban space is preserved at all levels of simplification.
doi:10.1145/1179849.1180012 dblp:conf/siggraph/ChangBZWPR06 fatcat:nwui6kpuenbxjauvooznkklssq