| The protection of cultural relics is in the contemporary and benefits in all ages.In the plan for the development of national cultural relics,it emphasizes strengthening the use of modern information technology and building a basic database of national heritage resources so as to digitally preserve national memories.In recent years,with the wide application of 3D laser scanning technology,coupled with the improvement of computer performance and the development of computer algorithm processing technology.It has provided an effective means for the digitization of ancient buildings and also brought opportunities and challenges to the digital modeling of ancient buildings.Pagoda is an important type of ancient Chinese architecture,and the Guanzhong region is one of the regions with more ancient pagodas in the country,with a high level of construction technology.Although the number of ancient pagodas preserved in the Guanzhong area is considerable and their research value is precious,they face the practical problems of poor technical accuracy of surveying technology,low technical informatization degree of construction parameters,lack of timeliness of protection and maintenance,and improper information feedback of ancient buildings.There are only a handful of surveyed ancient pagodas in the Guanzhong area,mapping data and detailed textual data archives.The paper on the ancient pagoda in Guanzhong has an important theoretical significance to carry out digital library construction technology research,through the use of 3D laser scanning for ancient pagoda digital data collection,access to valuable three-dimensional point cloud data and other basic data to form a complete and complete information,to master the overall characteristics and development of thedissemination context of the ancient pagoda.On the other hand.It is of great practical value to provide a reliable digital model for the research of graphic construction in the digital protection of ancient buildings.Based on the application of 3D laser scanning technology,this paper,by means of field mapping,data modeling,algorithm design and simulation experiment,has targeted the research and design of algorithms such as preprocessing,data restoration and feature extraction for the three-dimensional point cloud data of ancient pagoda in Guanzhong area.And then applied the 3d model of ancient pagoda in Guanzhong area to rapidly and accurately draw 2d graphics,excavate the high-width ratio relationship of buildings,and analyze the early model construction of seismic performance analysis.Finally,the basic information database of ancient pagoda and its visualization system were built,and the following work was carried out:(1)Proposed based on improved C-means algorithm and pagodas to point cloud bilateral filter denoising methods of three-dimensional point cloud data.During the collection of ancient pagoda three-dimension point cloud data,due to human interference,scanner defect,the impact of different factors such as surface smoothness,with small amplitude noise or outliers in the data,effects processing,making reconstruction model was rough or even deformed.In order to effectively remove the noise,keeping sharp features of the model(architectural detail of the Ancient pagoda),three-dimensional point cloud noise fall into two categories,namely large scale noise and small scale noise,using improved c-means algorithm and point cloud bilateral filtering algorithm for noise reduction fairing.Simulation results show that the algorithm can be used to remove larger-scale noise effectively as well as retain the valid data.In the meantime,massive data of 3D point cloud often consume large amount of computer time and space resources when being processed and displayed by a computer.Therefore,this paper constructs a point cloud data simplification algorithm based on regional space,which can simplify the data of ancient pagoda point cloud and improve the computer processing efficiency of point cloud data.(2)Proposed a method of boundary extraction and repair using non-closed holes.Because of the defects of the instrument itself and the partial occlusion of the object andother factors,it also results in some local holes in the original cloud point,which seriously affects the surface reconstruction.Therefore,hole repair is needed to obtain the complete model.In this paper,the boundary of the scattered cloud based on the connection of non-closed holes is used to determine the hole repair range.It can effectively avoid the closed hole,such as doors and windows,and extract the boundary point of the non-closed hole boundary point and the nearby model.According to the information of the hole and its surrounding point,An implicit surface is reconstructed based on the moving least squares method,and the implicit surface sampling is performed by a certain step to complete the hole repair.The simulation results show that the algorithm can repair the holes of this type,and the patched data can be fused with the original point cloud data to recover the original model.(3)Proposed the use of aIB algorithm based on mutual information theory to extract point cloud data characteristics.Due to the point cloud features can truly reflect the exterior architectural details of ancient buildings,feature extraction plays an important role in the process of 3D reconstruction of ancient buildings.Aiming at the problem that the scattered point cloud data acquired by laser scanning is difficult to extract the feature,the image is digitized by binary method and the feature data set is constructed.The aIB algorithm is used to obtain the feature of point cloud data more accurately while compressing the noise data as much as possible.Experimental results show that aIB algorithm can effectively improve the accuracy of point cloud data features.(4)Completed two-dimensional graphics rendering of the ancient ancient pagoda under the principle of respecting the authenticity of the building,combined with historical data and ancient pagodas multi-view images.And on this basis,through the data analysis,digging out the proportion of the ancient ancient pagoda built in the "golden triangle" relationship,so as to accumulate the experience of the proportion of ancient ancient pagoda construction research.The seismic performance analysis of the ancient pagoda three-dimensional model constructed in Guanzhong area by using 3D laser scanning technology was carried out.Compared with the ancient building surveying and mapping techniques used in the anti-seismic research of the ancient buildings,the modeling method based on the 3D laser scanning technology canaccurately survey and obtain the three-dimensional digital model of ancient pagodas and correct the loss of primitives caused by the format conversion and deformation,it can simplify and delete some details which are not necessary for the FEA in the specific circumstances and add internal components according to the actual need to forward modeling,import analysis software for analysis,analysis accurately Anti-seismic performance of ancient pagoda.The above applications are some useful attempts to study the technology of building the digital model library of ancient architecture.(5)Build up the database of ancient pagoda and its visualization system.The ancient ancient pagoda has survived more than a thousand years,natural disasters such as earthquakes,wind erosion damage,the foundation uneven settlement,body material degradation is inevitable,so the corresponding repair,reinforcement,correction of the conservation project has been ongoing and will continue to occur.In this process of repeated repairs,the appearance of the form and the structure of the changes in the material and component of the authenticity of the reduction is inevitable.Therefore,this article extracts in high precision standard and records the objective information on various aspects of ancient pagoda through the selection of database,function design,index technology and 3 d model visualization technology build pagodas basic information database,whether it is to guide future possible repair activities,or for follow-up of the accumulation of basic research materials,lay the foundation,are extremely important and urgent significance.This study provides the basic theory and core technology for the research on the digital model library of ancient architecture by using 3D laser scanning technology,which also provides the basic method for the data processing of the massive ancient building point cloud data. |
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