Ordinal Characteristics of Transparency
Edward H. Adelson and P. Anandan
AAAI-90 Workshop on Qualitative Vision (pp. 77-81)
Boston, MA; July 29 (1990)
Transparency can arise in images due to a number of different physical phenomena.
We have proposed a pre-physical level of representation in which a number
primitive images organized as layers combine together to form an observed image.
The ordinal relationships between the luminances at an X junction can be used
categorize the X junction as non-, single-, and double-reversing junctions. These
categories can be determined without precise measurements, and are robust against
point nonlinearities in luminance sensitivity. Non- and single-reversing
junctions support transparency; single-reversing junctions lead to an unambiguous
interpretation of depth-order of the layers, while non-reversing junctions leave
the depth-order ambiguous. Double-reversing junctions do not support
transparency. Propogation of these constraints can be used to rapidly restrict
the set of the legal interpretations of an image.