Texture-based watermarking of 3D objects

The goal of all current 3D object watermarking algorithms is to protect either the computer data representing an object's geometry or the intrinsic shape of a 3D object. Observing that these methods cannot protect the use of 3D objects in terms of visual representation, we propose a completely different approach, based on the texture of 3D objects. The idea is to watermark the texture of a 3D object and then be able to retrieve the watermark from any 2D representation of the object. Th is method works by reconstructing the object's texture from a given 2D view of it. For this, the rendering parameters must be known or estimated. After evaluating our algorithm in a controlled environment we thus propose a projective registration algorithm allowing us to accurately estimate the perspective projection used to produce a given 2D view. The last part of this thesis presents an algorithm for hiding the geometry of a 3D object into its texture image. The originality of this data-hiding algorithm is that the hidden information is intimately linked to the host information. We want to preserve this link of spatial coherence as well as ensure that the retrieved data degrades progressively when the host information is degraded. This is achieved through a spatio-frequential representation of geometry and texture, which are both represented as a function of cylindrical coordinates.