| In recent years,with the continuous development of 3D GIS(Three-Dimensional Geographic Information System)technology,the research on 3D digital urban architectural models has also extended from external structures to internal structures.Moreover,combined with the three-dimensional,hierarchical,internal and external integration of geographic information models,this research requires the implementation of fine-grained management of architectural models in threedimensional digital cities from macroscopic to microscopic and outdoor to indoor.However,in the internal structure of building 3D models,traditional modeling methods generally have problems such as low modeling efficiency,high acquisition cost,and low model accuracy.How to quickly acquire the internal and external structures of high-precision building models has become an urgent problem.BIM technology is a building information model based on the relevant information of construction projects as the basis of the model,using the open industry standards to digitally manage the physical characteristics,functional characteristics and related life cycle information of buildings.The resulting 3D building model can be used as an important source of 3D GIS indoor spatial data.In recent years,most of the researches have focused on the data fusion of BIM models defined in the International Common Standards IFC(Industry Foundation Classes)in the field of 3D GIS.In this paper,the IFC standard is used as the theoretical basis for the study of BIM technology.The OSGEarth open source 3D digital earth library is used as the 3D GIS platform to analyze the physical mapping relationship between the BIM model and the OSG model under the OSGEarth platform.The OSG model is created by analyzing the building model under the IFC standard,and the BIM model conversion algorithm is verified.The 3D visualization management of the BIM model in the 3D GIS platform OSGEarth 3D terrain scenes is realized.The main research contents are as follows:(1)Firstly,the BIM technology profile is introduced and compared with the characteristics of 3D GIS.After that,the IFC standard is selected as the research object of BIM models according to the requirements of the construction fields,and the geometric features and semantic features of the building entity based on IFC standard are analyzed.The IFC2X3 version is used as the data standard for studying the BIM model in this paper.(2)Taking the customized 3D model OSG data format under Open Scene Graph 3D rendering engine library as the research object,analyzing the data structures,scene organization structures and state rendering mechanism of OSG model.Secondly,based on the data analysis of the OSG file,the rendering and drawing of the 3D model is realized by combining the scene node organization structure of OSGEarth.(3)Combining the information mapping between the current IFC format and the OSG format on geometric information and semantic information in 3D modeling,this research explores a UBM unified building model that stores geometric data and attribute data as an intermediate model to implement BIM model to OSG.This study also discusses the converted BIM model applied to the basic spatial analysis algorithm in the OSGEarth scenes,and completes the data fusion algorithm between the BIM model and the OSGEarth digital earth rendering engine.(4)The research uses QT5.10.1 plus Microsoft Visual Studio2015 to develop the environment,and uses the Ifc Plus Plus open source parsing library and OSGEarth platform to build the “BIM model 3D visualization” experimental platform.Through a series of interactive experiments on data transformation,3D modeling and visualization,basic spatial analysis,etc.in the three fields of construction,building construction and HVAC equipment of the IFC building at different construction stages,the feasibility of the conversion algorithm is verified,which lays a foundation for the integrated application of BIM technology in the field of 3D GIS. |
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