Research On 3D Model Watermarking Algorithm Robust To Geometric Attacks

The rapid development of computer and Internet related technologies makes not only accessing multimedia products much convenient,but also raising issues,such as illegal copying,unauthorized usage and modification.There is the same problem of copyright protection for 3D models.With the development of virtual reality,cooperative design and Web 3D,copyright protection of 3D models is becoming increasingly urgent.In this dissertation,some 3D model watermarking methods are studied.The main research contents are as follows:Watermarking scheme robust to geometric attacks based on 3D point model is proposed.The invariant space coordinate system is established by using principal component analysis(PCA).The model is evenly divided many planes which are perpendicular to a coordinate axis.The distances between the vertices of the cross section and the intersection of the axis are calculated.Watermark is embedded by circular shifting vertix distances.Mesh pre-processing is not required in the algorithm.Experiments show that the scheme is fairly robust against attacks,such as affine transformation,resorting,and simplification and noise.Watermarking scheme based on the multiresolution analysis of 3D mesh model is proposed.The model is divided into three layers.A skeleton layer of the model is used to establish an invariant space.Watermarking information is embedded into the appropriate vertices that are selected from the medium-resolution layer of the model.The selection of vertices is based on the area of the local set of the vertex.The vertices in the high-resolution layer are reserved for resisting simplification and smoothing attacks.The curvature of the local set of the vertex determines the embedding strength of the watermark.The adaptive embedding strength and the choice of the embedding position can provide a suitable trade-off between good transparency and maximum robustness.The simulation results show that the method is robust against attacks such as noise,smoothing,simplification,and affine transformation while ensuring high visual quality of the watermarked model.3D mesh model watermarking scheme based on the Beamlet transform is proposed.The first step of method is to calculate tangent planes of the appropriate vertices according to 1-ring neighborhood of each vertex,and project the 1-ring neighborhood of the vertex onto its tangent plane.The Beamlet transform is applied to the binary image of the 1-ring neighborhood on the tangent plane.When a line segment is extracted from the image of the 1-ring neighborhood by using the Beamlet transform extract,the watermark bit will be embedded into the opposite vertex of the line segment.The line segments obtained from the Beamlet transform make watermark information reposition when the model is attacked.Experiments show that the usage of the Beamlet to construct watermark synchronized information is an effective way to improve the robustness of watermark.3D solid model watermarking scheme based on feature template and Surfacelet transform is proposed.The Surfacelet transform is applied to the 3D solid model.The coefficients of the Surfacelet transform are divided into several parts according to their energy distribution and each part has independent energy estimate and threshold.The coefficients with the most energy are selected to be embedded the watermark.Thus,the watermark can be embedded into significant region as well as highly textured region.The choice strategy of embedding position above effectively guarantees good transparency and maximum robustness of the proposed algorithm.The feature template consists of feature points which are extracted from the embedded model using improved Harris-Laplace operator and are robust to geometric deformation.When the model is attaked,we can obtain the transformation relation by calculating the corresponding feature points and realize resynchronization,i.e,recover the lost synchronism.Experimental results show the proposed algorithm has good transparency and is very robust to geometric attacks.