New spatial domain method for watermarking in 3D models

An invariable of affine transformation in 3D models, the Rate of Barycenter and Cross-point (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.