Computer Science, Information Technology and Telecommunications

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Browsing Computer Science, Information Technology and Telecommunications by Subject "Architecture--Details"

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    A three-step strategy for generalization of three-dimensional buildings modelled in city geographic markup language
    (Universiti Teknologi Malaysia, 2013) Baig, Siddique Ullah
    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