Legible Simplification of Textured Urban Models

Abstract

Mesh simplification and discrete levels of detail (LOD) are wellstudied areas of research in computer 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 applied to 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 an approach to simplifying city-sized collections of 2.5D buildings based on the principles of "urban legibility" as defined by architects and city planners. We demonstrate that our method, although similar to traditional simplification methods when compared quantitatively, better preserves the legibility and understandability of a complex urban space at all levels of simplification.

An Integrated Simplification Approach for 3D Buildings with Sloped and Flat Roofs

“…Referring to the original scenes, the three simplified scenes in each subfigure show no obvious visual difference, suggesting that the proposed approach is able to retain overall visual appearance of the cityscape even with a low LOD (e.g., LOD1). Compared to visualizing the cityscape with bounding boxes of original 3D buildings or simple cells (Chang et al, 2008;Glander and Döllner, 2009), the multi-scale cityscape acquired by our approach is much more realistic. The data volume reduction rate ranges from 61.1% to 97% (Table 2).…”

“…For example, the 3DCM of Charlotte, NC, contains approximately 370,000 3D buildings, or over four million polygons [8]. The problem is made more acute when users attempt to interact with the 3DCM to explore different parts of a city, which involves constant panning and zooming.…”

“…To tackle this challenge, existing studies have resorted to multi-scale representations [8][9][10][11]. In these studies, important buildings such as landmarks, buildings in the focus areas where users are interested in, or buildings which are near to the view point are visualized with 3D buildings in high levels of details (LODs) [12] while others are visualized in low LODs.…”

3D City Models and urban information: Current issues and perspectives

“…Other researches focused on different aspects. Chang et al (2008) presented a city scale simplification approach based on "urban legibility" intended for better preserving understandability. Guercke and Brenner (2009) proposed a framework for the generalisation of 3D city models, within which custom feature types and generalisation algorithms can be defined.…”

All range and heterogeneous multi-scale 3D city models

“…In the work of Mao et al [38], buildings are divided into clusters by the road network and grouped with their close neighbors in each cluster. Chang et al [39] presented a large scale simplification approach based on "urban legibility" intended for better preserving understandability for complex urban spaces at all levels of simplification. Guercke and Brenner [40] proposed a framework for the generalization of 3D city models, within which custom feature types and generalization algorithms can be defined.…”