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

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(a)<br />

(b)<br />

Figure 2.7. <strong>Face</strong> modeling using anthropometric measurements (downloaded<br />

from [35]): (a) anthropometric measurements; (b) a B-spline face model.<br />

be used <strong>for</strong> face modeling. For instance, Lengagne et al. [106] <strong>and</strong> Chen et al. [112]<br />

built face models from a pair of stereo images. Atick et al. [107] <strong>and</strong> Yan et al.<br />

[108] reconstructed 3D face surfaces based on the Karhonen-Loeve (KL) trans<strong>for</strong>m<br />

<strong>and</strong> the shape-from-shading technique. Zhao et al. [109] made use of a symmetric<br />

shape-from-shading technique to build a 3D face model <strong>for</strong> recognition. There<br />

are other methods which combine both shape-from-stereo (which extracts low-spatial<br />

frequency components of 3D shape) <strong>and</strong> shape-from-shading (extracting high-spatial<br />

frequency components) to reconstruct 3D faces [113], [114], [115]. See [116] <strong>for</strong> additional<br />

methods to obtain facial surface data. However, currently it is still difficult to<br />

extract sufficient in<strong>for</strong>mation about the facial geometry only from 2D images. This<br />

difficulty is the reason why Guenter et al. [117]<br />

utilize a large number of fiducial<br />

points to capture 3D face geometry <strong>for</strong> photorealistic animation. Even though we<br />

can obtain dense 3D facial measurements from high-cost 3D digitizers, it takes too<br />

much time <strong>and</strong> it is expensive to scan a large number of human subjects.<br />

48

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