A study on the Digital Watermarking and Copyright Protection Method for 3D Geometric Models

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The purpose of this research is to develop the new digital watermarking methods for 3D geometric models in the area of CAD, CAM, CAE and CG.Watermarking is one of the copyright protection methods where an invisible watermark is secretly embedded into the original data. The proposed watermarking method is based on wavelet transform and multi-resolution representation of the 3D geometric models.In this research, large-scale polygon, solid and surface models were firstly designed using commercial 3-D CAD systems. Then the series of operations consisting watermark embedding on these models, coordinate transformation and modification of models, and watermark extraction were executed in order to evaluate the performance of proposed watermarking method.The robustness of the watermark for external attacks, capacity of embeddable watermark and the geometric error caused by watermark embedding were evaluated quantitatively. The following results were obtained ;(1) The embedded watermarks were completely kept under the affine transformation.(2) The geometric error of the models caused by the embedding could be easily kept within the specified tolerances.(3) The embedded watermarks were robust to the several attacks such as noise superposition and vertex modification on the models.(4) The embedded watermarks were not robust to the cropping operation for the models.Furthermore, the developed watermarking method was improved so as to be applied to the watermarking for 2D vector data such as digital map. As a result of the experiment, it was verified that the visual quality of the data could be kept, the capacity of the watermark was large enough to store the copyright data, and the watermark was very robust to the noise superposition on the vertex coordinates.In the future, the modification of the algorithm will be necessary so that the embedded watermark becomes more robust to the cropping operation for the 2-D or 3-D geometric models.