Research On Bim Model Rendering Optimization Technology Based On Web3D

As a multidisciplinary information storage,sharing,exchange and management of collaboration,BIM technology can enable efficient collaboration among various participants and multi-disciplines in construction projects,improve project management efficiency,reduce project costs and shorten project construction cycle.BIM model is the basis of BIM technology and also the core of BIM technology.However,there are still problems such as low transmission efficiency,long rendering time and lagging browsing in the rendering display of large-volume BIM models on the Web.Therefore,in this thesis,we optimize the loading and rendering of BIM models on the web side to address the above problems.In the loading optimization,for the problem of long transmission time caused by the BIM model data transferred from remote server to client through network,the method of using local Indexed DB database cache for client is proposed.After the client loads the BIM model from the remote server and renders it for the first time,it will be cached to the local Indexed DB database,and then the model rendering will directly extract the data from the local database,thus reducing the transmission time of the BIM model data.By designing the local cache and remote server data synchronization scheme,the version comparison between local cache and remote server data is performed to ensure that the model data in the local cache is always the latest version.Meanwhile,in order to limit the problem that the local cache is too large,which leads to slow model loading,an improved LRU algorithm is proposed to clean up the local cache of BIM model data.In terms of rendering optimization,for the problems of low frame rate and lagging browsing of BIM model rendering,an octree based 3D scene model management data structure is designed to improve the efficiency of the paper’s view cone rejection algorithm;a two-layer view cone rejection algorithm based on the enclosing sphere and enclosing box is proposed to quickly reject most of the components that are not inside the view cone through the enclosing sphere based view cone rejection algorithm to speed up the view cone rejection The enclosing sphere based cone rejection algorithm can quickly remove most of the components that are not inside the cone,speed up the cone rejection algorithm,and improve the rendering frame rate of the model;the enclosing box based cone rejection algorithm can improve the accuracy of visibility cropping.Based on the view cone rejection algorithm and model interaction,the attention-based BIM component rendering priority ranking algorithm is proposed,the viewpoint prediction algorithm based on Elmit interpolation is designed,and the scheme of separating internal and external components of BIM model and dynamic rendering is designed.The attention-based component rendering prioritization algorithm prioritizes components according to their attention during model interaction,and improves user experience by accelerating the rendering of high-attention components.When the viewpoint is outdoors,only the outdoor components are rendered,and when the viewpoint moves indoors,the indoor components are dynamically rendered with the view cone rejection algorithm,which can significantly reduce the number of rendered components and improve the rendering rate of the BIM model.frame rate of the BIM model.Finally,the proposed algorithm and scheme are verified by several indexes,and the experimental results show that the BIM model data loading optimization scheme and rendering optimization scheme proposed in this paper can greatly reduce the loading time of BIM model data,improve the frame rate of BIM model rendering,reduce the memory occupation of BIM model,and thus improve the user experience.