Estimation of illuminant direction, albedo, and shape from shading
Zheng, Q.; Chellappa, R.
Pattern Analysis and Machine Intelligence, IEEE Transactions on
Volume 13, Issue 7, Jul 1991 Page(s):680 - 702
Digital Object Identifier 10.1109/34.85658
Summary:A robust approach to the recovery of shape from shading
information is presented. Assuming uniform albedo and Lambertian surface
for the imaging model, two methods for estimating the azimuth of the
illuminant are presented. One is based on local estimates on smooth
patches, and the other method uses shading information along image
contours. The elevation of the illuminant and surface albedo are
estimated from image statistics, taking into consideration the effect of
self-shadowing. With the estimated reflectance map parameters, the
authors then compute the surface shape using a procedure that implements
the smoothness constraint by requiring the gradients of reconstructed
density to be close to the gradients of the input image. The algorithm
is data driven, stable, updates the surface slope and height maps
simultaneously, and significantly reduces the residual errors in
irradiance and integrability terms. A hierarchical implementation of the
algorithm is presented. Typical results on synthetic and images are
given to illustrate the usefulness of the approach
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