Compression of parametric surfaces for efficient 3D model coding

In the field of compression, the type of 3D models traditionally considered is that of polygonal meshes, for which several efficient compression techniques have been proposed in the recent years. Nowadays, an increasing proportion of 3D models are created by a synthesis or modeling process, instead of captured from the real world. Such models are most often given as parametric surfaces, which have several advantages over polygonal meshes, such as resolution independence and a more compact representation. This paper proposes a method to code parametric surfaces, given as Non-Uniform Rational B-Splines (NURBS). The coding scheme consists in coding the NURBS parameters (knots and control points) using a predictive scheme, coupled with uniform quantization and entropy coding, The multiplicity of knots is preserved by decomposing the knot vectors in a break vector (the values) and a multiplicity map. The rate-distortion of the proposed scheme is evaluated and compared against compressed triangular meshes. The results show that a considerable compression ratio is achievable under visually lossless conditions, that outperforms by far triangular meshes. In addition of having a better rate-distortion performance, the coding scheme enables the efficient transmission of synthesized 3D models retaining their resolution independence.