基于Cesium 的地下三维管网3D Tiles 模型构建与可视化

Cesium作为目前日益流行的开源三维地图引擎,在各领域都有着广泛的应用前景.但目前原生Cesium不具备渲染地下管网模型可视化的条件.基于Cesium提出了一种利用shapefile二维地下管网数据自动构建三维地下管网3D Tiles模型的建模方法并完成了模型的可视化展示.具体步骤是首先将二维shapefile数据分级处理构建四叉树结构关系,通过迭代遍历各级的单块二维数据,将点、线要素分别进行逐瓦片的模型变换矩阵计算和模型构建,将点要素封装为i3dm模型,线要素封装为b3dm模型,得到3D Tiles地下管网模型;然后基于Cesium二次开发实现数据模型对接、地表透明化、裙摆关闭、摄像机地下视角等功能,完成模型的可视化展示.本方法使用辽宁省盖州市北海新区管网shapefile实例数据进行测试.结果 表明,二维地下管网shapefile数据能够快速生成3D Tiles模型,实现良好的地下三维模型可视化展示,为后续Cesium地下空间相关研究工作提供技术支持和方法参考,有助于完善B/S架构的地下空间三维可视化管理系统,支持数字孪生城市建设.

The 3D Tiles Model Building and Visualization Technology of Underground Pipe Network Based on Cesium

As a popular open-source engine of 3D mapping, Cesium has been widely applied in various fields. However, the native Cesium does not have the ability for rendering the visualization of the underground pipe network model. A new modelling method was proposed for constructing 3D Tiles model automatically based on 2D vector data of underground pipe network. On the basis of the above operation, the visual display of the model was carried out. In the processes of modelling, the 2D vector data was graded and processed to quadtree structure. The point and line elements were used to generate a corresponding model transformation matrix by traversing the point and line elements. The relationships between the model transformation matrixes and its corresponding standard models were then established. The point elements were encapsulated as an i3dm model, and the line elements were encapsulated as a b3dm model afterwards. The 3D tiles underground pipe network model was finally obtained. The visual display of the model was realized by docking of data and model, setting the functions of surface transparency, hemline closing, and composition of the camera''s underground perspective, which were based on secondary development of Cesium. The above model was tested and verified on the basis of the pipe network vector data of Beihai new area, which is located in Gaizhou, Liaoning province. The results show that 3D tiles model can be rapidly generated based on 2D underground pipe network vector data, and the underground 3D model can realize visualization display. It can provide technical support and method reference for the follow-up research on Cesium underground space. Furthermore, it can improve 3D underground visual management system of B/S structure, supporting the construction of digital twin cities.