| With the development of water conservancy projects informatization and Internet technology,the engineering visualization cloud platform based on Web GL and BIM technology has become an important tool for real-time browsing of engineering conditions and improving management.However,due to the high complexity of the BIM model and the strong closedness of the software,it is still difficult to display the data in the network completely.Aiming at these problems,this paper took Bala underground cavern group as the object to study the web BIM platform framework and the network transmission and rendering of BIM model.The main contents and achievements are as follows.1.The network visualization of BIM model was realized.and the network transmission speed was improved.Aiming at the high complexity,low transmission efficiency and strong closure of BIM model,3D Tiles was selected as the lightweight data format for 3D scene transmission and loading.With the help of Revit secondary development tool,lightweight processing of model reconstruction,component instantiation and geometric mesh simplification were carried out,which reduced the redundancy and file size of the model.Through the format analysis of gl TF and 3DTiles,the direct conversion of RVT to 3DTiles was completed while the model data information were fully retained.2.The scenario loading strategy for underground cavern group structure was designed.In order to reduce the rendering pressure brought by large-scale 3D scene to webgl pipeline,the dynamic loading strategy of the 3D scene was optimized,combined with the structure and distribution characteristics of the underground cavern group.By comparing and analyzing the LOD process in BIM and GIS fields,a dual LOD process mechanism that takes into account both the level of detail and development of the model was designed.In addition,by studying the structural characteristics and spatial division of the traditional pyramid index,a spatial index structure integrated various tree structures was designed which can automatically adjust the boundary.3.The system development and function expansion of 3D visualization cloud platform were realized.Aiming at the architecture defects of current cloud platform,ngnix load balancer and node nework server were introduced to improve the system’s ability to process concurrent requests and reduce the load-bearing pressure of application server on the basis of B/S mode.Based on Cesium Earth engine,a 3D visualization cloud platform of underground cavities was constructed with data source of the Bala hydropower station.In addition to visualization and interaction function,the functions of model cutting,hierarchical display of plant,spatial measurement and two-dimensional and three-dimensional linkage observation were designed for engineering requirements.Through the above research,this paper explored a feasible and efficient Web BIM cloud platform framework,which realized the network real-time visualization of BIM model of underground cavern group,and improved its transmission speed and rendering efficiency.In addition,the practical application value of the visualization cloud platform was improved through the extended design of the platform function,which provided technical support for the intelligent management of water conservancy and hydropower projects. |
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