Multi-Watermarking Algorithm For Three Dimensional Meshes

With the rapid development of the computer and network technology, transmission and reproduction of types of multimedia information has become very easy. But it will produce a serious of potentially dangerous, such as illegal possession, tampering, copying and other damage to the interests of the copyright owner. In order to protect copyright, digital watermarking technology is projected, and it develops very quickly. The traditional digital watermarking technology is based on 2D model, but a large number of 3D model has appeared in the network. Because of the unique features of three dimensional, the protection technology of the 2D model can not be directly used in the 3D model, so the digital watermarking technology based on 3D model is proposed and quickly become the research focus. After analyzing the research result of domestic and external digital watermarking technology on the 3D model, the watermarking algorithm of 3D meshes are researched based on the spatial domain. The main works include:(1) In this thesis, we state the development background of digital watermarking technology, research status and its applications. Then the core idea, the technical difficulties, key issues, common attack methods, and evaluation criteria for the 3D digital watermarking are introduced.(2) A robust watermarking is proposed based on 3D mesh models in this thesis, The scheme embeds the watermark by modifying the location of vertices in their related space. With this approach, the original model is not required during detecting watermarks. In order to improve robustness, the watermarking can be embedded repeatedly. Experimental results show that the algorithm has good visualizing quality and robustness which can be against the attacks such as translation, rotation, uniform scaling, model shearing and vertex permutation, but it is weak when attacked by non-uniform and noise.(3) A robust multi-watermarking is proposed based on 3D mesh models in this thesis. We have embedded the second watermarking by changing the vertex of triangular patches' order while maintaining normal vector of triangular patches. In order to increase the security of this algorithm, Arnold scrambling is processed to the image information before embedding watermark information, which make the watermarking become disorganized and more safety. Experimental results show that the second watermarking makes up the weakness of first watermark information, and has good visualizing quality and robustness to non-uniform and noise attacks, but has weakness to model shearing attack. Because these two watermark information are embedded to the one model, they can protect the model together. When one watermark information has been destroyed, the model can be protected by extract another watermark information to prove the copyright, which make the three dimensional model more safety.This thesis is supported by grant No.09YSY31 from Northwest University Graduate Innovative Education Project.