Rendering And Display Optimization Of Revit Architecture 3D Model Using WebGL

Revit Architecture is the currently mainstream 3D building software.This paper combined the Revit building model with WebGL aims to reconstruct and display the Revit Architecture 3D building model and discuss LOD optimization techniques based on Revit “famliy” object.The article focuses on Revit model transformation from software to browser,reconstruct model,query attribute and display performance optimization.Study carried out in four directions.(1)Converting Rvt model file to JSON format intermediate file.Geometry and attribute information contained in the file of the Rvt building model,private data format is not supported by the Web.Revit API will devide the geometry information and attribute information and convert the geometry information into OBJ format file,save in the geometry area and the property area which conotained in the JSON file.Then WebGL renders JSON file and reconstruct the building model.(2)Achieving the feature that using WebGL graphics library to rapidly prototype architecture in browser.Obj Loader library extracts the JSON model file and passes to the Three.js to redraw the model file in the browser.Using canvas setting to resize window resolution,repositioning the layout to enable fast rendering capability on the mobile device model.Those methods establish the foundation for 3D data application on mobile device.(3)Associated Rvt file geometry data and attribute data with UID to achieve the property querying and displaying functions in browser.Rvt file’s geometry data and attribute data are stored in OBJ model area and the property area in JSON file.Date is associated with UID.Clicking the browser to obtain a two-dimensional coordinate system.Using the z-axis from the nearest point of view can get the three-dimensional object and it’s UID.Traversing UID to associate model data with attribute data and displaying attribute date in the browser.It can query the sharp and attribute of building model,help user apart from Revit software,display model on mobile device by date association.(4)Combining with Revit "family" feature,this article proposes the LOD display optimization algorithm which based on the Revit “family” by the ratio of the Minimized Bounding sphere’s radius and distance.Revit API uses the "family" unit to processe Rvt model object,each instance of the object is stored as a subset of the OBJ file with the smallest bounding sphere algorithm to calculate bounding sphere radius and the sphere center coordinate.Using the ratio of the radius to the center of the sphere from the point of view as a control condition in LOD algorithm,achieving the purpose of saving computing resource.