Research On The Technologies And Algorithms Of 3D Mesh Models Digital Watermarking

With the fast development of digital media and Internet, the copyright protection of digital media has been an important research field. 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.Current watermarking technology focuses on still images, video and audio streams.But,more and more 3D digital media have been used in CAD/CAM, the straightforward demands are to prevent the 3D model from being used unauthorizedly. As a new way of the information copyright protection,digital watermarking will prossess extensive application perspective in this field.Based the study of three-dimensional watermark algorithm, a robust watermarking scheme for three-dimensional triangle meshes has been proposed. First,a transformation of the model to an affine invariant space was finished prior to watermark embedding. Second, calculate the distance of each vertex to the center of the mesh,get a sequence of real numbers which are the values of distances ,then consider the real number sequence as a digital signal in spatial domain and transform it to a signal in frequency domain using one-dimensional discrete fourier transform (DFT).Third, we embed a watermark into the signal in frequency domain,and then transformed it back to a digital signal in spatial domain.This new spatial-domain signal represents the new values of the distances after embedding a watermark.Finally, we modify the coordinates of the vertices to make their distances to the mesh center satisfy these new values. In affine invariant space, the 3D object is not affected by geometric transformations, such as translation, rotation and scaling.So the proposed method is robust enough to geometric transformations.Experimental results show that this watermarking scheme is robust against attacks such as mesh simplification, model cropping and random noise added to the vertex coordinates etc.Based the study of image zero-watermarking, a zero-watermark of there dimensional was proposed in this paper. In order to protect the copyright of three dimensional meshes, this algorithm constructs the watermark by the characteristic structure of there dimensional meshes instead of embedding watermark by altering the data of there dimensional meshes.The proposed method compromise the robustness and transparency of watermarked there dimensional meshes. Experimental results show the proposed method is simple to implement and fairly robust against common mesh attacks such as geometrical transform, mesh simplification, mesh cropping, random noise added to the vertex coordinates etc.