A Three-Dimensional Watermarking Algorithm Using the DCT Transform of Triangle Strips

Since it is easy to design robust and imperceptible watermarking algorithms against malicious attacks, most watermarking techniques insert watermark signals in the frequency domain. However, three-dimensional (3-D) geometric models have difficulties in natural parameterization for frequency-based decomposition. In this paper, we propose a new scheme for 3-D model watermarking in the DCT domain. In order to insert and extract watermark signals in the frequency domain, we traverse the 3-D mesh model to generate triangle strips and transform their vertex coordinates in the spatial domain into frequency coefficients in the DCT domain. Watermarks are then inserted into the mid-frequency band of AC coefficients for robustness and imperceptibility. We show that the inserted watermarks survive various attacks, such as additive random noise, geometry compression by the MPEG-4 SNHC standard, affine transformation, and multiple watermarking.