Wavelet-based blind watermarking of 3D models

Watermarking of 3D meshes has received a limited attention due to the difficulties encountered in extending the algorithms developed for 1D (audio) and 2D (images and video) signals to topological complex objects such as meshes. Other difficulties arise from the wide variety of attacks and manipulations 3D watermarks should be robust to. For this reason, most of the 3D watermarking algorithms proposed so far adopt a non-blind detection. In this paper we present a new blind watermarking algorithm for 3D meshes. In order to simultaneously achieve watermark imperceptibility and robustness a multiresolution framework is adopted. To do so we assume that host meshes are semi-regular ones, a property that permits to first perform a wavelet decomposition and then to embed the watermark at a suitable resolution level. Watermark detection is accomplished by computing the correlation between the watermark signal and the to-be-inspected mesh. Robustness against geometric transformations such as rotation, translation and uniform scaling is achieved by embedding the watermark in a normalized version of the host mesh, obtained by means of Principal Component Analysis. Experimental results show the validity of the proposed algorithm both in terms of imperceptibility and robustness against a wide class of attacks including noise addition, smoothing and cropping.