Biomedical Engineering Reference
In-Depth Information
Figure 5.5: Zheng-Chellappa's linear SFS algorithm applied to the synthetic
Mozart image. (a) is the input image with light source (
x
=
0,
y
=
0,
z
=
1). (b),
(c), and (d) are the reconstructed surface from three different directions.
domain, which will affect the accuracy of the linear approximation. (2) When
applying FFT and IFFT to the whole image, Pentland's algorithm needs more
time than Tsai-Shah's approach. Tsai-Shah's algorithm uses Newton's method
to solve the quadratic equations. When the initial value is close to the exact so-
lution, Tsai-Shah's algorithm converges very fast. Actually, given certain good
initial values, Tsai-Shah's algorithm needs several steps to converge. However,
it is well known that Newton's method cannot always guarantee convergence.
This disadvantage makes Tsai-Shah's approach sensitive to initial estimation
than Pentland's.
The discussion in this subsection has also shown us that the linear approach
is conceptually simple. The related algorithms are relatively fast and easy to
