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

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are listed in Table 2.2.<br />

All of these compression methods focus on model represen-<br />

Table 2.2<br />

Geometric compression efficiency.<br />

Method<br />

Geometric<br />

Compression [137]<br />

Topological<br />

Surgery [75]<br />

Geometric<br />

Loss Measure Compressed feature<br />

Compression<br />

Ratio (GCR)<br />

6–10 slight losses Positions, normals,<br />

colors<br />

20–100 no loss Connectivity;<br />

12–30 N/A Positions, facet<br />

properties;<br />

20–100 N/A ASCII-file sizes<br />

Remeshing [138] 54–1.2 Remeshing & compression<br />

tolerances<br />

Level of detail<br />

(facets)<br />

tation using triangular meshes. However, <strong>for</strong> more complex 3D shapes, the surface<br />

representation using triangular meshes usually results in a large number of triangular<br />

facets, because each triangular facet is explicitly described. We have developed<br />

a novel compression approach <strong>for</strong> free-<strong>for</strong>m surfaces using 3D wavelets <strong>and</strong> lattice<br />

vector quantization [139].<br />

In our approach, surfaces are implicitly represented inside<br />

a volume in the same way as edges in a 2D image. A further improvement in<br />

our approach can be achieved by making use of integer wavelet trans<strong>for</strong>mation [140],<br />

[141].<br />

53

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