Research On Open BIM Cross-platform Visualization Based On WebGL

BIM(BuildingInformationModeling),as the core technology of construction industry informatization,is clearly listed as the key technical area supported by the "13th Five-Year Plan".BIM visualization is not only the technical foundation of building informatization,but also determines the expansion space of other building management technologies.At present,most of the BIM visualization system is based on the C / S(Client / Server)architecture.This architecture visualization system has the defect of relying on the software platform and occupying very large computing resources during operation.,And cannot share resources through a browser.With the maturity of Web and WebGL technologies,BIM visualization system has moved from C / S architecture to B / S(Browser / Server)architecture.The B / S architecture visualization system is largely different from the C / S architecture visualization system.It does not require the installation of specific software and can directly use the browser to access the specified URL.The user can use BIM in different OS(operating systems)model.In addition,The adjustment of the data organization method and the lightweight processing of the B / S architecture visualization system not only ensure the stability of its use on terminals with different configurations,but also bring a smoother user experience under the premise of ensuring the digitization and informationization of the model.This article aims to achieve a lightweight display of building information models,combined with the IFC data exchange standard and WebGL three-dimensional visualization technology,theoretical research and application development of BIM visualization system,and completed the following work:First,it discusses the advantages and disadvantages of different architecture visualization systems when rendering models,proposes system development based on B / S architecture,and analyzes the overall and functional requirements of B / S architecture visualization systems.Then,by studying the IFC standard and IFC file data structure,the design of the IFC file analysis process is completed.While parsing the IFC file to obtain model information,parametrically reconstruct the geometry of the model component and triangulate the geometry to complete the design of the system file conversion module.The converted JSON format data is stored in the basic data list and the geometric data list of the class components,and the design of the system data storage structure is completed.Then,based on file conversion and data storage,three.JS was used to load JSON format intermediate files to achieve model overloading,and light sources and camera objects were introduced into Scene scene objects to achieve model shading and rendering.The model transformation is realized by changing the camera object parameters,the ray()function is created,and the association mechanism is established to realize model pickup and attribute query,and the design of the system model interactive function module is completed.Through the above design,the development of WebGL-based open BIM cross-platform visualization system was realized.Finally,a case study verifies the consistency,completeness,fluency and efficiency of the visualization system model display,the diversity and practicality of the model interaction function,and the friendliness of browser compatibility.The system solves the problem of lightweight and cross-platform BIM data,and realizes online browsing and information interaction of models and architectural drawings.