Research On Robust 3D Model Zero-watermarking

With the rapid development of the Internet,more and more digital products enter into the public network environment,the application is more and more widely,while the copyright protection problem of multimedia information in the network is also significantly increased.Digital watermarking technology mainly embeds copyright mark data into multimedia contents to ensure the safety of them.In recent years,with the development of 3D scanning technology and computer graphics as well as the improvement of computer performance,the maturity of 3D printing technology,the 3D model is also facing the problem of ownership protection.The existing 3D model watermarking technology,which is usually based on the vertex and face of the model,is difficult to resist resampling attacks brought with 3D scanning.Meanwhile,in order to balance the relationship between the robustness and transparency of 3D model watermarking,we propose a three-dimensional zero-watermarking algorithm based on integral invariant(Zero-watermarking uses the important features of models to construct watermark information,rather than modify the data of models to embed watermarks into models)in this thesis.The algorithm first preprocesses the model using CPCA(Continuous Principal Component Analysis)in order to realize the invariance of 3D models,such as translation invariance,scale invariance and rotation invariance.Secondly,the pre-processed model is grouped according to the Ray-Based method.Combining with the previous operation,the vertices on the model can be grouped in a fixed order.So that the watermark constructed from model after attack and the watermark constructed from original model can keep a certain synchronicity.Then,the neighborhood sphere is constructed separately in each packet,and the spherical integral invariants are calculated(here we propose two calculation methods spherical crown approximation method and spherical surface area-based method)and normalized.Finally,the watermark information is constructed by comparing the calculated value of the normalized spherical integral invariant with a threshold(usually 1/2).Once the watermark information is constructed,we need to register it together with a timestamp to a trusted third-party IPR database to achieve copyright protection for the 3D model.This technique solves the contradiction between the transparency and robustness of the invisible digital watermark.The experiment proves that the algorithm can resist the resampling attack well,and it has strong robustness against common attacks such as simplification,subdivision,smoothing,similarity transformation and vertex rearrangement.At the end of this thesis,a 3D zero-watermarking system based on the proposed algorithm is constructed.The system is based on VS2010,C++,MFC,OpenGL and Half-Edge data structure.The system mainly includes three functional modules,namely:model load module,model interaction and visualization module,watermarking algorithm and watermark information correlation calculation module.