Research On Multi-scale Expression Method Of Feature-Driven Urban 3D Model

Under the trend of vigorous development of digital cities,urban 3D models play an important supporting role in intuitive,accurate and highly diversified urban 3D scenes.In recent years,with the support of powerful technologies such as Web GL,remote sensing image reconstruction,laser scanning,image-based modeling and rendering,urban 3D models have also been widely applied and studied.The amount of urban 3D model data and related spatial data information is increasing rapidly,and users' demands for spatial cognition of urban 3D scenes are also increasing.How to combine the importance of urban 3D models and user attention and other spatial cognition characteristics to improve the rendering efficiency and user experience of urban 3D scenes is currently important one of the research topics.Aiming at the problems of the lack of multi-scale constraints,the design of expression rules dominated by user space cognitive needs,and the lack of priority expression and transmission in characteristic areas in the current serialized expression process of local objects in urban 3D models,this study starts from the urban 3D model,multi-scale representation theory,feature-driven evaluation model design,and urban 3D scene scheduling and rendering were studied,and a feature-driven multi-scale representation method of urban 3D models was proposed.In order to implement and verify this method,this paper independently designed and developed the urban the multi-scale expression display system of the 3D model realizes the multi-scale and efficient loading of the urban 3D model.The main research content and results of this paper are summarized as follows:(1)Literature review.Starting from the actual needs of urban 3D model expression and application,the research background and significance of this article are explained,and summarize the current research status of city 3D model expression methods as well as the ideas that can be used for reference in the expression of 2D maps and vector data.The current problems in the research of multi-scale representation of the city's three-dimensional model are discussed,the idea of ??feature-driven constraints is proposed,and the research content and overall thinking framework of this article are determined.(2)Theoretical research on multi-scale expression of urban three-dimensional model.An overview of the concept of multi-scale expression and related technologies,an introduction of standards and specifications related to the visualization of urban 3D scenes,and a summary of the ideas,classification and organization of multi-resolution level of detail models.(3)Feature-driven evaluation model design.Combining the characteristics of the urban3 D model with the user's spatial cognition,based on this,a quantitative evaluation index that measures the transmission priority of the urban 3D model-visual clarity is proposed,and it is applied to the design of the feature-driven evaluation model,which is designed for this article.The calculation of the index value is performed on the multiple scales of the urban based on the characteristics of their respective focus,which design and perfects the multi-scale expression rules of the urban three-dimensional model.(4)Designed a feature-driven multi-scale expression strategy for a urban 3D model.Taking the calculation results at various scales as constraints,precoding the urban 3D model,combined with network transmission-oriented dynamic scheduling and rendering technology of the urban 3D scene,realizes the feature-driven multi-scale expression of the urban 3D model.(5)Prototype system design and development.The method described in this article is applied and practiced,and a multi-scale expression visualization system of urban 3D model has been developed,and it has been used in actual engineering projects.