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1 Introduction In constructing the percept of transparencyseeing an object or surface through a

Summary: 1 Introduction
In constructing the percept of transparency÷seeing an object or surface through a
partially transmissive surface÷the visual system must decompose or scission (Koffka
1935) the light intensity at each retinal location, and assign the separate components
to distinct surfaces in depth. The contributions of the underlying surface and the trans-
parent surface are collapsed onto a single intensity value at each point in the image,
and these contributions must be separated if the two surfaces are to be extracted. In
this regard, the problem of perceptual transparency is similar to other visual problems
in that multiple contributions (eg surface reflectance, illumination, surface orientation)
must be inferred from a single pattern of light intensities. What makes perceptual
transparency unique, however, is that the image decomposition involves the visual
construction of two distinct surfaces (or material layers) along each line of sight.
Figure 1 demonstrates the problem of transparency: The display at the left is seen as a
black-and-white surface with an overlying mid-gray partially transmissive surface÷even
though each point in the image contains a single gray-level value. Each light-gray patch
in the display is thus decomposed into a mid-gray transparent component and an
underlying white component, whereas each dark-gray patch is decomposed into mid-
gray and underlying black. If the same light-gray and dark-gray patches are seen in
isolation (right side of figure 1), no such decomposition occurs, and each patch is seen
as opaque.


Source: Anderson, Barton L. - School of Psychology, University of Sydney
Singh, Manish - Department of Psychology, Rutgers University


Collections: Biology and Medicine