Shape quality measurement for 3D watermarking schemes

Alface, P.R. Macq, Benoît [UCL]

Shape quality assessment is a new challenge for a wide set of 3-D graphics applications and particularly for emerging 3-D watermarking schemes. In order to measure distortions new metrics have to be drawn between an original 3-D surface and its deformed version. These metrics are necessary to determine whether a deformation is perceptually acceptable and therefore whether this deformation should be considered while testing the robustness of a 3-D watermarking scheme. In this paper, we propose an objective metric based on the comparison of 2-D projections of the deformed and original versions of the shape. Rendering conditions are carefully specified as they play a key role on the human perception of the 3-D object. We compare the behaviors of this objective metric and of state-of-the-art metrics to subjective human perception for a set of deformations caused by watermarking schemes and usual watermarking attacks on several 3-D meshes. The protocol of these subjective psychovisual experiments is presented in detail. We discuss these experimental results for the purpose of the benchmarking of 3-D watermarking schemes.