The Modeling Technology Research Of Underwater Measurement Data With Incomplete Geometric Features

The modeling technology of underwater measurement data with incomplete geometric features is an important part of reverse engineering CAD modeling technology.By obtaining the data information of the tested object through underwater measurement,this technology can reassemble the damaged and incomplete area according to the characteristics of the existing data,so as to restore the original appearance of the tested object.With the rapid development of interdisciplinary research and digital design technology,the rapid prototyping quality and efficiency of underwater cultural relic can be improved by applying the modeling technology of underwater measurement data with incomplete geometric features.Considering that the most of underwater cultural relics are bowl-shaped broken pieces,this paper focuses on the 3D underwater measurement,the inner surface identification of bowl-shaped broken pieces,the screening of the best broken pieces to be matched,the reassembly strategy of the broken pieces set and so on,which provides a technical guarantee for the 3D measurement of underwater objects and the reassembly matching of broken pieces.A 3D measurement system of underwater data with incomplete geometric features is designed to meet the technical requirements of underwater measurement and 3D modeling.The system uses CCD industrial camera and LightCraft 4500 optical projector to complete the underwater measurement of structured light based on the phase-shifting method,which can combine the underwater calibration data and the phase information of grating projection on the 3D object to obtain the point cloud of the tested object.The system has the characteristics of real-time detection and simple operation.It provides basic data for the subsequent research of reassembly matching technologyThe bowl-shaped broken pieces reassembly algorithm based on the inner surface characteristics can effectively avoid the over segmentation problem caused by the fracture surface,but its difficulty lies in the accurate extraction of the inner surface.Therefore,an identification algorithm for inner surface of bowl-shaped broken pieces combining point cloud proportion and smoothness is proposed.Firstly,according to the significant difference of point cloud proportion,the inner surface and the outer surface are identified from the segmented surface group.Then,the inner surface of bowl-shaped broken pieces is extracted by the difference of smoothness value.The experiment shows that this algorithm can accurately extract the inner surface of bowl-shaped broken pieces.Moreover,its surface recognition accuracy and average operation speed are 20.00%and 144.63%higher than the traditional surface roughness method.In order to assist the computer to realize the automatic screening for the best matching pair of broken pieces,this paper uses the distinct inner surface features of bowl-shaped broken pieces and proposes a screening method for bowl-shaped broken pieces combining the extended Gauss sphere(EGS)model and similarity.This method establish the EGS model based on the color feature and the characteristic circular curvature,aimed at screening out the best matching pair of benchmark broken pieces.The experimental results show that the screening accuracy of the method can reach 93.87%.Additionally,compared with the establishment method of traditional EGS model,the accuracy and efficiency of this method are improved by 6.60%and 16.08%respectively.Owing to the large number of broken pieces,there are many mismatches in the reassembly process of broken pieces sets.In order to solve this problem,according to the screening basis of the best matching broken pieces,a reassembly strategy of broken pieces based on the inner surface features is proposed,which can eliminate the mismatches and aviod the failure of reassembly.The experiment confirms that this strategy can successfully complete the whole assembly of broken pieces sets,thus assisting the computer to automatically complete the reorganization and matching of broken pieces sets,which provides a complete 3D model data for the rapid prototyping of bowl-shaped cultural relics at the same time.Additionally,this strategy is highly suitable for bowl-shaped broken pieces with distinct geometric or color features.