Research On Digital Watermarking Technologies For 3D Geometry Models

The information exchange based on computer networks has provided great convenience to the usage and spreading of the digital multimedia products. However, the digital products can be illegally copied and tampered with ease, which makes the information security and copyright protection become a practical problem needed to be solved urgently. 3D mesh models are being used widely as a new type of media, and the problems of copyright protection and content authentication have become the hotspots of 3D mesh processing. Digital watermarking technology provides digital products with an efficient measure of copyright protection. The main research work of this dissertation is:Firstly, state of art watermarking technologies for 3D mesh models. The basic concepts, the category methods, the representative algorithms and the attacking measures of 3D watermarking schemes were briefed.Secondly, two robust watermarking schemes for 3D mesh models are proposed. One scheme is based on dividing the 3D mesh using umbilical points, with an automatic selection of umbilical points that are robust against surface remeshing. These points are then used as seeds in the partition of the shape into fast approximated Delaunay geodesic triangles. The other scheme is based on holistic feature points, an automatic selection of intrinsic feature points and uniform resampling vertices of each patch using a reference plane are principle contributions. A 3D mesh model is divided into patches taking feature points as centroids.. Tremendous experiment results show that watermarks embedding with these two watermarking schemes are imperceptible and robust against various attacks.Thirdly, in this dissertation, the advanced parametrization techniques which served in Digital Geometry Process are introduced into 3D mesh watermarking, current mature 2D watermarking schemes are applied to 3D models so as to obtain higher embedding capacity, quicker processing speed and appears more robust. And a novel planar parametrization algorithm which behaves better than existing methods is proposed. In addition, the problems which emerge in this application are explained in a great detail in this paper. Experiment results show that watermark embedding with the watermarking scheme is imperceptible and robust against various attacks.In the end, a study on 3D watermarking information-theoretic model based on game theory is presented in this paper. In this dissertation, the discussions on 3D watermarking capacity are applied to planar parametrized 3D mesh models. Actually, it is still an analysis of 2D watermarking capacity but based on 3D distortion measures. In addition, a parallel Gaussian channels model is set up based on AC coefficients from the host normal-map image data transformed by Block-DCT. The formula of the capacity is given, and the curves for the relationship between the distortion and channel capacity illustrated.