Research And Implementation Of Bridge Model Display System Based On Web GL

Since 2002 the BIM(Building Information Modeling,BIM)technology had been proposed,it has been widely used in the world.The construction management of bridges gradually changed from two-dimensional to more visual and intuitive threedimensional management.The current bridge model shows that the system is mostly Client-Server architecture,but the architecture has many problems,such as difficulties in mobile office,high maintenance and upgrade costs.With the development of Internet and Web GL(Web Graphics Library)technology,web developers can use system graphics cards to smoothly display 3D models and scenes in the browser.Although this technology is not yet perfect,it has the advantages of low threshold,convenience,and low cost compared to the traditional way.Therefore,it is very promising to study the smooth display and interaction of the 3D bridge model on the Internet.In this thesis,a continuous beam bridge is taken as the research object to explore the process of bridge model from modeling to web side smooth display,and realize the functions of bridge model establishment,import and load,web side model reconstruction,interactive operation and roaming.The completed research work mainly includes:(1)The bridge model was established with Revit2018,and its data structure was analyzed.A special plug-in was designed and developed,which can extract the attributes and geometric information of the BIM model and save the data information in Json format.(2)Load bridge BIM model in Json format by using Web GL technology,design and implement an edge contraction algorithm based on curvature and side length,and apply this algorithm to the model’s LOD(Levels of Detail)optimization,then combine with asynchronous calls,visual volume removal and other methods,solve the problems of slow speed and poor effect of the actual model in the process of loading and rendering.For the incomplete transmission problem that may occur in the large model,this paper utilizes the method of resuming the breakpoint to improve.(3)Based on the related algorithms of computer graphics,the interactive methods with the bridge BIM model are designed and realized,including scaling,dragging,rotation and other operations.Explore and realize the function of roaming on the model.Based on the above research results,a bridge BIM model display system based on Web GL was developed.Compared with the use of professional 3D modeling software to view the model,the system reduces the precision by about 5%,but improves the fluency by about 30%,and greatly improves the convenience.