Research On Digital Watermarking Of 3D Mesh Model

Copyright protection of digital products has become more and more important with the development of Internet technology and 3D printing technology.The huge compensation involved in the copyright dispute cases that have occurred in recent years has caused a sensation in the society.Designers and developers in different fields are looking for effective copyright protection methods.As an important model widely used in the field of three-dimensional digital,the threedimensional mesh model has important research significance and practical significance to protect its intellectual property with digital watermarking technology.The thesis aims at the problem that the 3D mehs model cannot mark visible information such as copyright after the entity is printed,and adopts the method of embedding visible digital watermark to realize the printing of the entity's copyright logo.Compared with image watermarking,the watermarking of 3D mesh model is more vulnerable to affine transformation attack and anti-cropping attack.The thesis uses double watermarking method to improve the robustness of watermarking.The main research work includes:(1)Aiming at the disadvantage that the current 3D model watermark is only visible on the model and not visible after printing,a 3D model visible watermarking algorithm based on bitmap font was proposed.First,bitmap fonts are used as input watermark information.Then,based on the bitmap font,the smooth area of the 3D model is selectively subdivided and projected onto the 2D plane.Next,embed the watermark information into the 2D plane and project the corresponding area onto the original mesh.Finally,the watermark is embedded at a certain intensity so that it is still visible after the 3D printing of the model.The experimental results show that the watermark information including Chinese characters,English characters,numbers and icons are visible on the printed entity and is robust to common attacks.(2)Aiming at the problem that a single type of watermark cannot effectively resist multiple attacks,a contour-controlled vertex-resistant 3D model-based double watermarking algorithm was proposed.Two different types of watermarks are embedded in a three-dimensional mesh model: one is a watermarking algorithm based on contour point segmentation and DCT transformation.This algorithm can well resist cropping attack,but because it embeds the watermark into the coordinate values last bit,so the resistance to signal attacks and affine transformation attacks is poor.The other is a watermarking algorithm based on the redundant information of the 3D model.This algorithm does not change the spatial position of the model vertices.It is very robust to signal attacks and affine transformation attacks,but it relies on the topological structure of the 3D model.Therefore,resistance to cropping attack is poor.Because the two watermarking algorithms have different requirements for the embedding position of the model,the two watermarking algorithms can be integrated together to form a robust that is resistant to both cropping attack,signal attacks,and affine transformation attacks,and will not mutually noisy watermarking algorithm.Experimental results show that the watermarking scheme proposed in this paper not only maintains good transparency of 3D model watermarks,but also resists common attacks such as affine attacks(translation,rotation,scaling),file attack,signal attacks(noise,smoothing),and cropping attack.(3)A 3D model watermarking system with high robustness was developed.This system is based on two watermarking algorithms proposed in this thesis.This system using a data stream-oriented design method,it implements four functional modules: a visible watermark embedding function based on bitmap fonts,and a double watermark embedding and extraction function that is resistant to cropping attack.3D model visualization and interaction function,3D model simulation attack function.And use the black box test,the test results show that the system meets various functional requirements in the system requirements,and has achieved the expected purpose.This paper proposes a visible 3D model watermarking algorithm based on bitmap fonts for 3D printing,a dual watermarking algorithm based on contourcontrol vertices and a three-dimensional model robust watermarking system,which effectively solves the problem that visible watermarks cannot exist on entities.The existing invisible watermarking algorithm is not strong against cropping attack.The developed 3D model watermarking system has certain use value and promotion significance for the copyright protection of 3D models.