GPU ray casting method for visualizing 3D pipelines in a virtual globe

Pipelines are an important part of urban infrastructure development.As part of a virtual globe(VG),the high-efficiency and high-quality visualization of 3D large-scale and high-density urban pipelines is of great importance.This paper proposes a GPU-based pipeline ray casting method for the visualization of urban-scale pipelines in the framework of a VG.The method involves the initial partitioning of the pipeline data into tiles,based on the relationship between the pipeline layer scale and the discrete global grid system(DGGSs).The pipeline centerline in each tile is then segmented and encoded,and a coarser pipeline bounding volume is subsequently constructed using a geometry shader.Finally,the fine 3D pipeline is rendered using a pixel shader.The results of the experimental implementation of the proposed method show that it satisfies the requirements for the multiscale visualization of pipelines in a VG.Moreover,compared with the traditional polygon-based method,the method facilitates a 20%increase in rendering frame rate for the same pixel level accuracy display effect.It also enables the visualization of the thickness of the 3D pipeline without any obvious effect on the rendering efficiency。