Enhancing the experience of 3D virtual worlds with a cartographic generalization approach (original) (raw)

2007, The Visual Computer

In this work we propose a new approach for fast visualization and exploration of virtual worlds based on the use of cartographic concepts and techniques. Versions of cartographic maps with different levels of details can be created by using a set of operations named cartographic generalization. Cartographic generalization employs twelve operators and domain-specific knowledge, being the contribution of this work their transposition to 3D virtual worlds. The architecture of a system for 3D generalization is proposed and the system is implemented. Differently from traditional cartographic processes, we use artificial intelligence for both selecting the key objects and applying the operators. As a case study, we present the simplification of the historical quarter of Recife (Brazil).

A THREE−STEP STRATEGY FOR GENERALIZATION OF THREE−DIMENSIONAL BUILDINGS MODELLED IN CITY GEOGRAPHY MARKUP LANGUAGE

For a better visual impression, three-dimensional (3D) information systems and landscape architectures need photo-realistic visualization of detailed 3D datasets. But easy accessibility with efficient rendering becomes difficult due to the detailed data associated with 3D objects. Therefore, different applications demand different levels of detail (LoD). A single generalization method cannot be applied to remove or preserve different pieces of building information on a certain LoD. Additionally, different generalization strategies produce different results for generalized models. Therefore, the aim of this thesis is to contribute the state-of-the-art in 3D generalization methodologies. This thesis proposes a 3D generalization framework based on a three-step (projection, generalization and reconstruction) strategy to generate less-detailed and more abstract representation of buildings modelled in the City Geography Markup Language (CityGML). The proposed strategy focuses specifically on simplification and aggregation of building footprints based on point-reduction, edge-removal and small circle strategies. Furthermore, vertex reduction method for simplification of complex shapes of building footprints is one of the contributions to the scientific field of 3D Geographic Information System (GIS). Experiments and results of the thesis show that 3D generalization based on the CityGML generalization specifications can avoid removal of important features of a building and fulfill the demands of task specific applications. Furthermore, mostly, data reduction is directly proportional to the length of edges as threshold value. However, the data volume of the generalized models is 10.5% for 4 meters and 30.62% for 6 meters threshold values. About 37.65% of data is reduced after generalization at LoD1 CityGML model as compared to 30.18% at LoD2. Furthermore, 3.31% boundary of building footprints of Putrajaya at 5 meters threshold value is observed as eliminated despite removing 52% smaller edges. The authenticity of generalized models is evaluated based on a comparison of similarity between original and generalized boundaries of building footprints. The proposed generalization strategy could be extended to generalize a group of buildings and maintain topological relationship among generalized LoDs.

Three-Dimensional city model visualisation for real-time guided museum tours

The Photogrammetric Record, 2004

ABSTRACT Nowadays, there is a trend to show different kinds of cartographic data (and related information) not only in 2D but also in 3D. Additionally, all the data must be easily accessible through the Internet, interactively, and preferably in real time. All these requirements make the management and visualisation of huge volumes of geographical information complicated, mainly in urban areas. This paper deals with these issues and prepares the reader to overcome them. Furthermore, a methodology is proposed for visualising large 3D city models when photogrammetric data and existing geographical information systems arc available. Finally, a real-time interactive animation is introduced, which provides guided museum tours with the aid of the 3D city model of Valencia. © 2004 The Remote Sensing and Photogrammetry Society and Blackwell Publishing Ltd.

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