Face Detection and Modeling for Recognition - Biometrics Research ...

2.3.3 3D Model Compression
Among various representations of 3-D objects, surface models can explicitly represent
shape information and can effectively provide a visualization of these objects. The
polygonal model using triangular meshes is the most prevalent type of surface representations
for free-form objects such as human faces. The reason is that the mesh
model explicitly describes the connectivity of surfaces, enables mesh simplification,
and is suitable for free-form objects [136]. The polygonization of an object surface approximates
the surface by a large number of triangles (facets), each of which contains
primary information about vertex positions as well as vertex associations (indices),
and auxiliary information regarding facet properties such as color, texture, specularity,
reflectivity, orientation, and transparency. Since we use a triangular mesh to
represent a generic face model and an adapted model, model compression is preferred
when efficient transmission, visualization, and storage is required.
In 1995, the concept of geometric compression was first introduced by Deering
[137], who proposed a technique for lossy compression of 3-D geometric data.
Deering’s technique focuses mainly on the compression of vertex positions and facet
properties of 3-D triangle data. Taubin [75] proposed topological surgery which further
contributed connectivity encoding (compression of association information) to geometric
compression. Lounsbery et al. [76] performed geometric compression through
multiresolution analysis for particular meshes with subdivision connectivity. Applying
remeshing algorithms to arbitrary meshes, Eck et al. [138] extended Lounsbery’s
work on mesh simplification. Typical compression ratios in this line of development
52