A Lightweight Method For Railway Tunnel BIM Model With Semantic Constraints

The integration of railway tunnel BIM models in a 3D GIS environment is a key technology for the information management of railway tunnel projects.As the number of long tunnel component-level BIM models with massive amounts of data and tens of kilometers of railway tunnel BIM models in a 3D GIS environment to achieve efficient organisation of scheduling and visualisation applications becomes a challenging problem.Current high-precision complex railway tunnel BIM models are modelled with reference to a single level of detail and are typically organised in a parametric structure,whereas model data in a 3D GIS environment is frequently described at multiple levels of detail and is typically organised in a triangular grid structure,with the difference in data structure resulting in an increase in geometric data after the BIM model is converted to a GIS model.Concurrently,there are variations in the division of the scale of railway tunnel model components in the 3D GIS common standards,leading to challenges in visualising the railway tunnel BIM model directly in the 3D GIS environment following the common conversion and organisation.This paper addresses the aforementioned issues by conducting research on semantically constrained BIM model lightweighting methods for railway tunnels,designing a semantic mapping and geometric multi-detail level conversion method in response to the demand for multi-scale visualisation of railway tunnel BIM models in a 3D GIS environment,and achieving efficient organisation and scheduling of multi-detail level models.The precise contents of the research are as follows:(1)Generation of semantically constrained multi-detail hierarchical models for rail tunnels.(1)Generation of multi-detail models for railway tunnels with semantic constraints.The railway tunnel BIM model is analyzed in terms of macro-regional scale,mesoengineering scale,and micro-construction surface scale visualisation application needs.(2)Organization of geometry-semantics-attribute information and visual scheduling of multi-detail hierarchical models for railway tunnels.Design the 3D tile data structure encompassing the geometry-semantics-attribute data of the railway tunnel 3D model,formulate the hybrid LOD data loading rules for the railway tunnel multi-detail hierarchical model,and implement the 3D tile organisation and scheduling method for the railway tunnel multi-detail hierarchical model.(3)Prototype system for railway tunnel scene visualization and experimental analysis Build the underlying prototyping system platform based on the Digital Twin Lens platform software DTScope.Using the actual Kangding No.2 railway tunnel BIM model as the data source,the data were divided into three categories: "no-detail hierarchical model," "multidetail hierarchical model," and "semantically constrained multi-detail hierarchical model." Three data sets were compared and analyzed in terms of frame rate indicators for visualisation.The results of this paper indicate that the semantically constrained multi-detail hierarchical model of railway tunnels has better overall rendering performance in multiscale visualization applications and can meet the requirements of efficient organization and scheduling of multi-detail hierarchical models in 3D GIS environments and highperformance visualization applications..