Showing papers on "Object model published in 1977"

Visual information for object identity in apparent movement

Abstract: Apparent movement is used to examine the nature of the visual information which specifies object identity. Constructive feature-comparison theories rely on static formal information and predict that two phases of an apparent movement display must be featurally similar in order to appear as a single object in motion. An opposing Gibsonian model is based on abstract geometrical information and predicts that the two phases may differ radically in shape but must be ecologically transformable in order to be seen as a single object. The predictions are tested by presenting subjects with displays which are similar but not transformable, and transformable but dissimilar. Results show that the transformability of the display determines its perceived object identity, while featural similarity has no effect. An event theory of object identity is offered which claims that theaffordance structure of an event, determined by geometric invariants specifies object identity. ma-

Model MTF for Conventional X-ray Imaging Systems

Abstract: A simple MTF formula for the X-ray imaging process has been derived taking into account the size of the X-ray focus, off-focus radiation, scattered radiation from the object, and position of the imaged layer within the object. This formula has been confirmed experimentally using a lead test raster. It refers to an object model consisting of a variable depth object layer within a homogeneous water medium.