Parity enhanced topology based spot area watermarking method for copyright protection of layered 3D triangular mesh data

Summary A parity enhanced topology based spot area watermarking method is proposed to embed information in objects with layered 3D triangular meshes such as those reconstructed from CT or MRI data. With the integration of parity checking, it improves the robustness against unauthorized alteration of a single bit in every consecutive 8-bits of length. Watermark message is cut into several pieces and each piece of message is embedded at different spots so that if a piece of message is lost in one spot, the same information can be potentially retrieved from other spots by error correct decoding. The method compares height of the vertices of a triangle lying in the same layer. A watermark message is converted into a binary bit sequence, a parity bit is added with every consecutive 8 bits, and then embedded into the model in either way that the first vertex of a triangle in the upper level or in the lower level, that carries information 1 or 0, respectively. For experimental purpose, a watermark message is embedded in a mouse embryo model. It is robust against translation, rotation, arbitrary re-sectioning, local deformation, scaling, and unauthorized alteration of a single bit in every consequent 8-bits length. It is useful for shape sensitive 3D geometric models. It left some artifacts after re-arrangement of local or global numbering. These artifacts have vertices sorted in descending order in terms of degree. These unique features can also be used for 3D data retrieval.

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