Graphics Reference

In-Depth Information

In Chapter 5, we have discussed how to generate face animations using geo-

metric MUs. To augment the synthesis with appearance variations, we propose

to decide the texture blending coefficients based on the corresponding geometric

MUPs. The intuition is that geometry and appearance are correlated such that

partial information about appearance can be inferred from the corresponding

geometry. In similar spirit, Zhang et al. [Zhang et al., 2003] have demon-

strated the effectiveness of synthesizing facial expression appearance details

from given geometry.

Compared to [Zhang et al., 2003], the geometry part of motion is fully de-

rived from our geometric-model-based synthesis. Thus we can design a simpler

formulation for the blending coefficients. In this scenario, the problem is to find

an appropriate texture given geometric shape:
s
. Suppose the corresponding ge-

ometric MUP is and the exemplars' geometric MUPs are

We define the blending the coefficient as

where is a constant which normalize the sum of blending coefficients to 1. In

practice, we need to avoid the blurring of the blending result. For this purpose,

we adjust the value of the constant experimentally such that there are only

N
,
(N < K)
nonzero blending coefficients. Other coefficients are small and

can be set to zero.

4. Summary

We have described methods of face synthesis based on the flexible appearance

model. In particular, we have discussed two issues: (1) how to synthesize

illumination effects in face appearance; and (2) how to synthesize appearance

variations in face animations. The main contribution of this chapter is that we

show that our flexible appearance model can be used for synthesis in a flexible

way. More specifically, It means we can synthesize appearance variations based

on the model across different people and illumination environments.

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