Blind 3D Mesh Watermarking via Cylindrical Coordinate Transformation
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Solution Overview
Problem
Existing three-dimensional mesh watermarking techniques are ineffective in maintaining copyright protection for three-dimensional printing and scanning environments, as they fail to operate robustly against distortions caused by the printing and scanning processes, and require reference to the original model for watermark detection.
Innovation Solution
A blind mesh watermarking method and apparatus that embeds a watermark using a printing axis estimation technique, allowing detection without the original model by aligning the three-dimensional model, transforming the coordinate system, and embedding the watermark in a direction orthogonal to the printing direction, and detecting periodicity in the noise pattern to identify the printing direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing three-dimensional mesh watermarking techniques are used, then watermark embedding is possible, but the watermark cannot be detected robustly after printing/scanning distortion
Solution Approach 1:
The patent transforms the coordinate system from Cartesian to cylindrical coordinates, changing the parameter representation of the three-dimensional model. This parameter transformation allows the watermark to be embedded in a manner that is invariant to printing/scanning distortions, as the cylindrical coordinate system naturally accommodates the radial symmetry of layered manufacturing artifacts.
Solution Approach 2:
The patent embeds the watermark in the radial dimension of the cylindrical coordinate system rather than in the axial or tangential dimensions. This dimensional choice ensures that the watermark is perpendicular to the printing direction and thus not affected by stair-step distortions that occur along the printing axis.
2Measurement precision
If non-blind watermark detection method is used, then watermark detection performance is excellent, but original model information is required which increases system complexity
Solution Approach 1:
The patent enables the watermarked model to carry its own watermark information independently without requiring external reference to the original model. The watermark is embedded in a manner that allows self-detection through correlation analysis, eliminating the need for a database of original models and making the system autonomous.
Solution Approach 2:
Instead of requiring the original model to detect the watermark (non-blind method), the patent inverts the approach by designing a blind detection method where the watermark can be detected without the original model. This inversion is achieved by embedding the watermark in the radial component which maintains its characteristics after distortion.
3Ease of manufacture
If watermark is embedded in printing direction, then embedding is simple, but watermark is affected by stair-step layering distortion
Solution Approach 1:
The patent creates an asymmetric relationship between the watermark orientation and the printing distortion by embedding the watermark in the radial direction (perpendicular to printing direction) rather than parallel to it. This asymmetric positioning ensures that the watermark does not align with the stair-step artifacts generated during layered manufacturing.
Data Source
AI summary
In a watermark embedding method and apparatus, a layered three-dimensional model is aligned in a printing direction based on a layering direction of the layered three-dimensional model. Then, a watermark having a predetermined pattern is embedded into the aligned three-dimensional model in a direction orthogonal to the printing direction so that the embedded watermark is not associated with the printing direction.