Method Of Rapid 3D Modeling And Dynamic Updating For Large-scale Railway Alignment Real Scene

3D modeling of large-scale railway lines is the basis of 3D visualization design of lines.With the development of oblique photogrammetry technology,3D modeling technology of real scene has become a research hotspot.However,the widespread application of oblique photogrammetry technology has brought a large amount of realworld 3D survey data,resulting in a rapid increase in model complexity.The existing technology uses a CPU-based serial modeling method,which has low modeling efficiency and is difficult to modify after the model is built.,so it cannot meet the dynamic design requirements of real3 D visualization.In this regard,this paper proposes a CPU-GPU collaborative rapid modeling method,establishes the principle of minimum influence domain determination,studies a non-destructive cutting method of real 3D terrain based on the over-excavation-backfill strategy,and realizes the dynamic combination of railway line model and real terrain,which solves the problem of rapid 3D modeling and dynamic updating of large-scale railway lines.The main research contents are as follows:(1)Based on Open Scene Graph,a three-dimensional custom entity model of the line is constructed.The model integrates the horizontal,vertical and horizontal design information of the line,and uses the dragger technology to establish a horizontal,vertical and horizontal linkage adjustment mechanism,which realizes the modification of any one aspect and automatically triggers the linkage response adjustment of the other two aspects.(2)A CPU-GPU collaborative modeling method is proposed,which builds a 3D model of the line based on the cross-section sequence,defines the 3D model constructed by adjacent sections as a primitive model,and divides the sections into regular sections(bridges and tunnels)according to the type of structure.And irregular sections(roadbed),a CPU-GPU section modeling task allocation mechanism is established:CPU is responsible for processing irregular sections,and uses thread pool technology to build primitive models in parallel;GPU is responsible for processing regular sections,and the two work together to complete the line quickly.modeling.At the same time,the scene tree and hash table are constructed to realize the efficient management and fast search of primitive models.(3)The principle and method for determining the minimum influence domain are established,and the idea of transforming the 3D influence domain determination process caused by the line position modification into the determination of the 2D cross section influence set is proposed,and then the local 3D update is driven by the 2D section.The fast determination method of the cross-section influence set is studied,and the quadratic hash table search strategy is proposed,which realizes the fast search and update of the primitive model in the influence domain.(4)The template testing method in the graphics rendering pipeline is introduced,and the three-layer structure of the oblique photography layer,the mask layer and the skirt layer is proposed.The deletion of the slice,although "over-excavated" part of the terrain outside the boundary at this time,greatly reduces the traditional method of retrieval,positioning,and reconstruction of the calculation amount,and then uses the skirt layer to "backfill" the over-excavated boundary and the given boundary.Finally,the non-destructive integration of the real 3D terrain and the 3D model of the railway line is realized.Compared with the traditional method of directly modifying the triangulation,this method adopts the method of partial patch hiding and local triangulation reconstruction to complete the stitching,which has the advantages of less computation,faster stitching,and basically no damage to the original terrain.(5)Using the theories and development ideas,osg 3.4.0 was selected as the basic graphics development platform,and osg Earth 2.8.0 was used as the real 3D terrain data processing tool to develop a real 3D route selection design system for railway lines.Taking the railway as an example,the theories and methods proposed in this paper are experimentally verified.The test results show that the theory and method proposed in this study can realize the rapid modeling of large-scale railway lines and the dynamic refresh of models in interactive modification 3D visualization design requirements of railway lines.64 Figures,6 Tables,64 References...