Abstract: | In this two-part article we review viewer-centred representations in human and machine vision. Viewer-centred representations model objects through a number of views, each of which depends on the relative position of object and sensor. The main reference frame is centred on the viewer, so that the object's appearance changes with the view. In the first part of this article we discuss viewer-centred representations in machine visions, i.e. aspect graphs and allied representations. Approximate visibility techniques are especially important for applications, whereas exact aspect graphs feature mostly in research literature. We review also applicative work in sensor planning using visibility-based methods.
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