A Secure Image Based Watermarking for 3D Polygon Mesh

The proposed watermarking algorithm is based on geometrical properties of 3D mesh. The vertices of 3D mesh surface are categorized into flat, peak and deeper region. We first compare the perceivable distortion due to watermark insertion in the vertices of deep surfaces and the vertices belonging to either flat or peak surfaces. Our comparative analysis shows that insertion of watermark in deeper surface have less distortion in comparison to watermark insertion in flat and peak surfaces. In view of the fact, these vertices are categorized into three mutually exclusive groups. The first group (S1) is composed by the vertices of deeper area. For obtaining the vertices of second group (S2), the vertex normal is represented in IEEE-754 representation and n bit of mantissa is considered as ‘1’. The third set (S3) contains the remaining vertices. The vertices from S1 and S2 are selected for watermark embedding according to the secure code, which is obtained from hash function applied over the secure image (I). The vertices of S3 remain intact. The watermark embedding is done by re-positioning the selected vertices from their original positions according to the category they belong to. The robustness is assessed against different distortion and distortion-less attacks. The subjective (MoS) and objective (Hausdorff distance, RMS) assessment of watermarked object are also done to measure the extend of similarity between original object and watermarked object.