MESHGRID—A Compact, Multiscalable and Animation-Friendly Surface Representation

Abstract

Abstract-MESHGRID is a novel, compact, multiscalable and animation-friendly surface representation method, which has been introduced in MPEG-4 [1]. The MESHGRID representation attaches a description of the "global connectivity" between the vertices on the object's surface (i.e., the 3-D connectivity wireframe) to a regular 3-D grid of points (i.e., the reference grid). MESHGRID efficiently encodes the 3-D connectivity wireframe by using a new type of 3-D extension of Freeman chain-code. MESHGRID does not explicitly store the polygons of the surface, since the 3-D connectivity wireframe has particular connectivity properties allowing for the unambiguous derivation of the triangulation. The reference grid is a smooth vector field defined on a regular discrete 3-D space. This grid is efficiently compressed by using an embedded 3-D wavelet-based multiresolution intra-band coding algorithm. MESHGRID can be efficiently exploited for QoS since it allows for three types of scalability in both view-dependent and view-independent scenarios, including: 1) resolution scalability, i.e., the adaptation of the number of transmitted vertices; 2) shape precision, i.e., the adaptive reconstruction of the reference grid positions; and 3) vertex position scalability, i.e., the change of the precision of known vertex positions with respect to the reference grid. Furthermore, in addition to the classical vertex-based animation, MESHGRID also supports specific animation capabilities, such as: 1) rippling effects by changing the position of the vertices relative to corresponding reference grid points and 2) reshaping on a hierarchical basis of the regular reference grid and its attached vertices.

Transform domain texture synthesis

“…We are currently looking at the implementation optimisation of the algorithms. We are also in the process of applying the idea to handle the texture synthesis part omitted from consideration in the fast MESHGRID coding algorithm of [11], which has been one of the key contributions to the MPEG-4 AFX coding standard. This is expected to extend the applicability of the MESHGRID algorithm to full, fast, multi-scalable 3D object/surface coding.…”

“…The above features specifically make it viable for the proposed texture synthesis algorithm to be used in association with the progressive 3D surface coding and transmission algorithms, such as MESHGRID [11], considered within the MPEG-4 AFX standardisation activities [12].…”

“…Comparison of results: (a) Efros and Freeman's algorithm, (b) our previous algorithm[8], (c) Kwatra[11] and (d) proposed algorithm.…”