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Transparency and Occlusion Barton L. Anderson

Summary: Transparency and Occlusion
Barton L. Anderson
University of New South Wales
One of the great computational challenges in recovering scene structure from images
arises from the fact that some surfaces in a scene are partially obscured by nearer surfaces
or media. Both occluding and transparent surfaces interrupt the projection of more
distant surfaces, and may be considered two ends of a continuum. Occluding surfaces
completely obscure the surfaces that they occlude, whereas transparent surfaces only
partially obscure the surfaces they overlay. The degree to which a transparent surface
obscures an underlying surface depends on its transmittance (i.e., the proportion of light
that it lets through of the underlying layer). Thus, when the transmittance is zero, the
near surface is an opaque occluder; when it is greater than zero, some light of the
underlying layer is transmitted. In order for the visual system to recover scene structure
in contexts in which the transmittance of a near layer falls between zero and one, it must
decompose the image into a "layered" representation that specifies the presence of
multiple surfaces (or a surface and intervening media) along the same line of sight. This
form of decomposition has been termed scission.
In addition to the relationship between transparency and occlusion, the physical
transformations induced by transparent surfaces are intimately related to the physical
transformations that are caused by changes in illumination. This suggests that possibility


Source: Anderson, Barton L. - School of Psychology, University of Sydney


Collections: Biology and Medicine