Research On Fine Modeling Method Of True 3D Model Based On Oblique Photography

Since the concept of digital earth has been put forward, the world has set off a wave of digital, digital cities have mushroomed. The 3D model of urban building is an important part of digital city, the traditional way is use 3DMAX modeling software to carry on the manual modeling,in this way long period, high cost, slow to update.Tilt photography technology emerging to a wide range of regional features automatic modeling, it's fast and low cost, but the tilt photography modeling can't object-oriented analyze and not conducive to the analysis of three-dimensional geographic information.Therefore,urban modeling faces the contradiction between modeling efficiency and model analysis.In order to solve this contradiction, this paper presents a new modeling scheme, it can be used to build a model of buildings in a large scale. It is fast, low cost and can be object-oriented analysis. Specific work is as follows:Firstly, the data source of modeling method is tilted photographic image, the image is processed to generate the city point cloud , including: (1)aerotriangulation,calculate azimuth information of images; (2)dense image matching, generate the city point cloud model.And then obtains the necessary information of the building model through the point cloud data processing, including: (1)Point cloud filtering, distinguishing between the ground point and the non-ground point and obtaining the digital elevation model through the ground point interpolation; (2)point cloud classification, extract the building point cloud from the non-ground point, and extract building elevation information from the building point;(3)building contour extraction and regularization,extract the roof shape of the building from the building point cloud .Finally, based on the acquired building information, building a object-oriented building model using an interactive modeling system, including:(1)building LOD-1 mold, according to the building roof shape and elevation information, the roof will be stretched into a building LOD-1 mold,the scale and the space position of the model is the same as the real one; (2)In order to meet different accuracy requirements, support for fine revision of the model based on oblique images;(3)texture mapping, according to the building model coordinate position and tilt image orientation information, select the best building texture, and map to the building model surface,the method has the advantages of small amount of texture data, simple structure and convenient to modified.This paper summarizes the 3D virtual scene modeling technology in digital city,and proposes a different modeling scheme, which greatly improves the modeling speed and model authenticity while maintaining the detail. The research results have some practical significance to the process of digital city.