A Framework for Generalization of 3d City Models Based on Citygml and X3d

In this paper, a novel framework for generalization of 3D city models based on CityGML and X3D is proposed. In the proposed framework, the CityGML files are first parsed into a Java environment to acquire the city model information using Citygml4j, an open source Java API. Generalization is then performed in the Java environment. The outcome of the generalisation is CityTree, a multiple representation data structure of the objects, based on which we can effectively realize the continual scaling and dramatically reduce the load time of 3D models. Finally, the X3D representation is generated from the CityTree Model and is displayed by Xj3D viewer. By utilising CityTree, the multiple representation data structure, it is possible to have dynamic zoom functionality in real time. The paper describes the general framework and an implementation using this framework on the aggregation of 3D building objects. The implementation confirms the applicability of the framework for generalization of 3D city models. * Corresponding author. Bo Mao; [email protected]; phone 46 8 790-7676; fax 46 8 790-8580