一种新的三维模型水印嵌入空域算法

提出一种三维模型的仿射变换不变量——重心交点距离比(RBC),并基于该不变量提出了一种在三维模型中嵌入水印的空域方法——MICT方法.在嵌入过程中,该方法首先算出模型的重心,然后利用加速的顶点和重心连线与模型求交的方法,求得连线与模型的交点,从而计算出重心交点距离比.通过修改一个三角形面片3个顶点对应的RBC,依次嵌入Mark、Index、Content字符.为增强水印的鲁棒性,将水印字符串进行了多次嵌入.在提取过程中,为了提高字符提取的准确性,采取了投票的方法,对水印字符串的每一个字符,在256个字符中进行投票,得票最多的作为正确的字符.该方法是盲提取方法,简单实用,从理论上能够抵抗仿射变换、顶点乱序以及一定程度的噪声攻击等常见的三维模型水印攻击,并且在实验上得到验证.另外文章还对此方法的嵌入容量进行了分析和实验.

A New Spatial Domain Method for Watermarking in 3D Models

An invariable of affine transformation in 3D models,the Rate of Barycenter and Crosspoint(RBC) is proposed,and by using the invariable,a spatial domain method for watermarking in 3D models,called MICT method,is proposed.In the embedding process,this method first calculate the barycenter of the model,then after getting the line through the vertex and barycenter,it adopts the fast ray tracing method and gets the crosspoint of the line and the model.By modifying the RBC of the vertices,the Mark,Index,Content characters are embedded.In order to improve the robustness of the method,the watermark string is embedded multi-times.In the extracting process,we adopt the voting method to improve the accuracy of the extracted watermark,that is voting from 256 characters.For every character of the watermark string,they set the most voted character in the 256 characters as the right character.This method is a blind method,simple and useful.Theoretically,the embedded watermark is unchanged under some normal operations to the model such as affine transformation,vertex reorder and so on,and it can also resist some noise attack.The experiments have proved that it is robust under these operations.They also analyze embedding capacity by experiments.