Lightweight Research And Implementation On BIM Models Of Ancient Architecture Based On WebGL

In the era of “Internet Plus”,BIM technology,as a new technology and new concept of the construction industry,has gradually become an indispensable technology for visual analysis,dynamic simulation,and collaborative decision-making in the protection of ancient buildings.In order to fully explore the value of BIM and advance the BIM era towards the BIM Plus era,the study on the lightweight display of BIM models has become a new highlight and hot spot under the “Belt and Road” National Strategy and “Internet Plus”.The research work of this article relies on the National Natural Science Foundation project of "Research on Digital Protection and Restoration of Ancient Buildings in Ming and Qing Dynasties Based on BIM".The main tasks are as follows:(1)For the urgent need for lightweight BIM ancient building models,the BIM lightweight system was analyzed and designed in general.(2)Perform secondary development of Revit software to convert Revit models from RVT format files to JSON format intermediate files.The RVT-format architectural model data cannot be directly used in the web-end development process.Therefore,the secondary development of the Revit software is required,so that the geometric information and attribute information of the model are saved in the intermediate file of the JSON format,and then through the WebGL technology,the model is reconstructed and rendered.(3)Using the 3D GPU rendering principle of WebGL technology,through the development of WebGL,the reconstruction and rendering of the Revit 3D architectural model on the browser side;at the same time,the interactive operation of the Three.js framework is used to realize the interaction of the model on the Web side and ensure the consistency of the model displayed on the PC side and the mobile side.(4)The method of associating geometric data with attribute data in the JSON model file is proposed so as to realize the query and display functions of the browser-side model attributes.When the user clicks on the model element object,the ID can be obtained and its attributes can be displayed to implement the attribute query function,thus satisfying the user’s need for lightweight BIM.(5)Through a specific example of ancient architecture,this paper validates the lightweighting of BIM;the indoor positioning technology was studied and an indoor positioning method combining iBeacon and PDR was proposed;the combination of indoor positioning technology and architectural 3D visualization system provides support for the realization of tourism attractions and surrounding environment display as well as tourism guidance,which further enhances the application of the system.