Research On Lightweight And Visualization Of BIM Model Of Subway Signal Equipment

With the rapid development of the new generation of information technology with BIM(Building Information Modeling)technology as the core,it has become an inevitable trend to use BIM technology to promote the construction of digital urban rail transit.The signal system is an indispensable part of the post station system of urban rail transit.It is crucial to apply BIM technology to achieve the informatization construction of signal systems.Due to the wide variety and large quantity of signal equipment BIM models,as well as the long opening time and poor browsing,the models cannot meet the requirements of human-computer interaction and real-time rendering display.Therefore,the lightweight processing of the BIM model of signal equipment is a key problem to be solved in the application of BIM in the signal field.In this regard,this thesis proposes lightweight and visual research on the BIM model of subway signal equipment.The main research contents are as follows.(1)For the modeling of subway signal equipment,firstly,through research and analysis,the source of modeling information acquisition,modeling content,modeling method,and modeling process are determined.Secondly,the modular modeling method is used to divide the components of subway signal equipment into units,and the construction of the BIM model family library of subway signal equipment is completed.Finally,a semi-automatic modeling method is proposed for the generation of internal components and layout of cabinets with strong regularity.This method utilizes Revit’s API(Application Programming Interface)to automate repetitive modeling work and achieve rapid modeling.(2)A lightweight processing scheme for the BIM model of subway signal equipment is proposed by studying the lightweight method of the BIM model.Based on Revit secondary development tool and Visual Studio 2019 platform,the scheme is carried out from three dimensions: model necessary data extraction,appearance geometry data simplification,and file compression.For the necessary data extraction part of the model,the necessary geometric spatial information and semantic attribute information of the model are extracted by using the idea of digital-analog separation.The geometric information of the model is stored in the gl TF format file,the attribute information is stored in the My SQL database,and the unique ID of the element is used as the primary key.For the simplification of the geometric data of the model appearance,the improved QEM(Quadric Error Metrics)algorithm is used to reduce the number of triangular faces that make up the model.For the file compression part,the Draco compression algorithm is used to compress the model gl TF file.Finally,the BIM model of subway signal equipment with different complexity is selected as the experimental object to verify the feasibility and effect of the scheme.The experimental results show that the scheme can significantly reduce the amount of data in the model without losing the detail features and appearance size of the model.(3)The visual display and interactive operation of the BIM model of subway signal equipment on Web are studied.Firstly,through the research and analysis of common opensource frameworks in Web GL technology,Three.js is selected as the rendering framework of the BIM model of subway signal equipment in this thesis.Then use Java Script technology,HTML5(Hyper Text Markup Language 5)technology,and CSS(Cascading Style Sheets)technology to complete the development of the rendering engine on the Visual Studio Code platform.And the engine is used to realize the visual display of the lightweight subway signal equipment BIM model based on the Web.Then,on this basis,the interactive operation of the BIM model of subway signal equipment is realized by adding mouse click events and button control events.In addition,the ray intersection principle is used to realize the function of picking up highlight and attribute information query of model components.Finally,experimental verification and performance testing are conducted.The results indicate that the rendering engine developed based on Three.js can effectively achieve lightweight display of subway signal equipment BIM models on web pages,and interactive operation functions such as querying model attribute information are well implemented.