Multiple illuminant direction detection with application to imagesynthesis
Zhang, Y.
Yang, Y.-H.
Trident Microsyst. Inc., Sunnyvale, CA;
This paper appears in: Pattern Analysis and Machine Intelligence, IEEE Transactions on
Publication Date: Aug 2001
Volume: 23,
Issue: 8
On page(s): 915-920
ISSN: 0162-8828
References Cited: 17
CODEN: ITPIDJ
INSPEC Accession Number: 7020728
Digital Object Identifier: 10.1109/34.946995
Current Version Published: 2002-08-07
Abstract
Pentland observed (1982, 1984) that the human eye is sensitive to
the change of intensities. On an image of a smooth surface, the change
of intensities is maximal whenever the illuminant direction is
perpendicular to the normal of the surface. This motivates us to
introduce the concept of critical points, where the surface normal is
perpendicular to some light source direction. Apparently, the illuminant
direction has a simple geometric relationship with the corresponding
critical points. In this paper, for simplicity reasons, we restrict our
discussions to the shading of a Lambertian sphere of known size in a
multiple distant light source environment. A novel global representation
of the intensity function is derived. Based on this intensity
characterization, the least-squares and iteration techniques are used to
determine critical points and, thus, the light source directions and
their intensities if certain conditions are satisfied. The performance
of this new approach is evaluated using both synthetic images and real
images. As an application, we use it as a tool to determine light
sources in real image synthesis. The experimental results show that this
technique can be used to superimpose synthetic objects with a real scene
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