Research On Simplification-Based 3D City Model Generalization Algorithms

Developments such as computer graphics,technology of virtual reality,and three-dimensional modeling language standards allow an easy modeling and visualization of three-dimension scene.At the same time,along with the wide application of 3D city model,complex 3D scenes with large amount of data caused a great burden to visualization,and brought contradiction between the limited hardware conditions and costs of manpower and material resources.For applications such as analysis in GIS,the aggregation level of 3D models are not conducive to the analysis and extraction of data.On the contrary,a less detailed representation may be more applicable.The LOD technology arise to fix those problems.There are two approachesto creating LODs.The one is to create each LOD independently,which may cause saltation and discontinuity when models switching.The other one is that a coarser LOD representation is derived from a more detailed bringing switching of LODs more fluency,which is suitable for reality.Therefore,it is necessary to study algorithm for generalization of 3D city models.Algorithm of 3D city model generalization has four aspects of contents including trade-offs,simplification,displacement and summarization.Based on the CityGML data,this paper analyzes those four aspects of simplification in 3D and purpose a multiple representation structure called SimpTree which performssimplification in detail,mergence,typificationand exaggeration to generalize the 3D City models andrealize dynamic visualization according to the change of viewpoint.As to above,this paper mainly focuses on the following:1.Simplify the LOD1 models.2.For the landmarks,the exaggeration method was performed respectively togeneralize the 3D city models.3.For the adjacent and grid distributed buildings,the mergence and typification means were implemented to generalize those models.4.Create the SimpTree to store those store the different representation of the generalization and to realize dynamic visualization.5.Design and implementation of of 3D city models Generalization system.