Research On Digital Watermarking Of 3D Geometry And Its Application In CAD Product Copyright Protection

Digital productions facilitate the distribution and storage of information. But the copyright of digital productions must be protected. Digital watermarking is a way for copyright protecting. More and more research about watermarking is doing. Current watermarking technology fours on image, audio, video and text. The problem of watermarking 3D models received less attention. In contrast, the problem of watermarking 3D models has received less attention from researchers. But, more and more CAD-based 3D data is entering the World Wide Web. Accordingly, companies or copyright owners who present or sell their products in virtual space will face copyright-related problems. The straightforward demand is to prevent their 3D-based material from unauthorized use. As a new way for the protection of information copyright, digital watermarking will possess extensive application perspective in this area.Firstly, in the thesis, the basic principle and the domestic and oversea research status of digital watermarking technology are introduced briefly, such as, the basic concepts, the category method, the representative algorithms and the attacking measures. Based on the theoretical research of CAD product modeling method and the mathematical model of CAD product, the paper analyzed the denotation of CAD geometric model and the appliance of parametric surface and subdivision surface in CAD, narrated subdivision surface modeling which based on triangular meshes.Secondly, reviews the related works techniques for 3D geometrical CAD produce data, analyzes the features of CAD produce on the data use. Discusses the requirements of watermarking and types of the information redundancy of CAD produce data, and points out the remaining problems of the CAD produce watermarking techniques and proposes some research directions and key issues in the field in future. Generalizes the typical watermarking algorithms for CAD produce data and their merits and drawbacks. In allusion to the structural feature, some differential watermarking algorithms which adapt to CAD products. Thirdly, kind of subdivision mode called Loop has been analyzed specifically, some improvements also been presented based on subdivision watermarking algorithm in order to fit for the particularity of CAD products. In order to enforce the robustness of the watermarking surface algorithm, some improvements would be presented. Subdivision mode as a method of discrete surface from the existent rules unifies the representation between traditional parametric surface and polygon solid surface. With the increasing demand of smoothing surface modeling of arbitrary topology surface in computer graphics and other fields, subdivision mode can produce the complex topology surface and deal with the arbitrary control meshes in contrast to the NURBS surface, which could used to protect the copyright of 3D geometrical CAD products.Fourthly, At last, the experimental results of the algorithm are given to test the robustness of algorithm proposed in this thesis. Tremendous experimental results are presented in prove that the digital watermarking algorithm proposed in thesis, and the results thesis is unperceivable and shows great robustness against a variety of attacks such as rotation, nosing, mesh cropping and sorts of combination attacks.Finally, a search for 3D geometry CAD produce copyright protection is referred in this dissertation. There are a lot of job to do for the watermarking algorithms for CAD produce, not only the kind of the algorithms but also the number and the practices of the algorithms, some new the techniques also should apply to the 3D geometry CAD produce copyright protection.