The last decade or so has been witness to the increasing utilization of 3D information for modelling and representation purposes. This has also necessitated the development of techniques that can protect the ownership rights and prevent unauthorized usage or tampering of 3D data. 3D representation is completely digital, which means the multi-DRM techniques used in DRM protected content can easily be applied to 3D scene depictions.
However, an exception to the easy migration of general DRM solutions for 3D data is encountered in the field of data hiding. Various approaches used for video watermarking in 2D multimedia cannot easily be extended to 3D content. 3D video files have various attributes such as color channel, stereo objects, and depth prospective, which need to be analyzed while embedding a watermark.
Video watermarking techniques can be grouped into two major classes: Spatial domain watermarking and frequency domain watermarking. Spatial domain techniques embed the watermark in the frames of a video by directly modifying the pixels, while frequency domain watermarking modifies the coefficients of the transformed video frames according to a predetermined embedding scheme. Similar to 2D watermarking techniques, 3D watermarking too has shown better efficiency in frequency-domain techniques.
3D watermarking techniques can be broadly classified into the following categories:
- Geometry watermarking: In this technique, three fundamental components of a scene, the geometry, the texture, and a map that defines the relation between geometry and texture, are considered. These components are used in relation to the lighting conditions of a scene while forming an arbitrary view during rendering applications.
- Texture watermarking: The main goal of texture watermarking is to extract the watermark, that is originally hidden into the texture of the 3D object, from the rendered images or videos (obtained after projection of 3D object into 2D image planes), thus protecting any visual representation of the object
- Image-based Watermarking: Here, a scene is represented by only the 2D projection of the scenes, which are the images captured by cameras. While the first two methods protect the watermark information for the two important components of 3D scene representation (geometry and texture), this technique approaches this problem, as the watermarking of image sequences that are recording the same 3D scene and extracting the watermark from any rendered image, generated for an arbitrary view angle.
