Research Of 3D Mesh Digital Watermarking

Digital watermarking,which provides a scheme for copyright protection of digital media,has become a hot spot in the research field of multimedia data security in recent years. With the development of 3D digitalization and the increasing popularity of VRML language,3D mesh is to become a full-fledged multimedia type of graphics models. Focusing on the watermarking research of the mesh,the author proposes a new watermarking approach for appearance attributes and develops a new ICP (Iterative Closest Points) variant of mesh registration based on the framework of PM (Progressive analysis.This thesis describes a watermarking algorithm targeting on appearance attributes,the potential watermarking primitives. Generalizing shape watermarking to appearance attributes presents the major challenge that the watermarking for appearance attributes has more constraints. To solve the overflow or underflow of the components of appearance attributes caused by watermarking,we clip the error ones to the correct ranges by adjusting the corresponding basis function elements. The normalization operation would destroy the watermark embedded in the normal vector. The author presents a novel approach by rotating the normal vector around a fixed axis,which will modify its orientation,not magnitude. Results show that with preserving the appearance during the watermarking,the proposed scheme effectively improves the capacity and enhances the robustness of mesh watermarking.The ICP algorithm is widely used for mesh alignment and registration. To improve the performance of the traditional ICP method for the large data models of mesh watermarking,this thesis develops a new ICP variant based on the framework of mesh multiresolution analysis. The author presents a novel method for acquiring the initial approximate transformation in terms of the distribution feature of points around the centroid. This iteration in the new variant includes the following improvements,the strategy for selecting some set of points,rejecting certain pairs and weighting the corresponding pairs by both the shape and appearance attributes. Results demonstrate that the proposed algorithm for mesh registration,which can be integrated naturally with the mesh watermarking toolbox,works very well on the author proposed watermarking system for appearance attributes.