: Hannah M. Dee & Paulo E. Santos (2011): The Perception and Content of Cast Shadows: An Interdisciplinary Review, Spatial Cognition & Computation, 11:3, 226-25Recently, psychologists have turned their attention to the study of castshadows and demonstrated that the human perceptual system values information fromshadows very highly in the perception of spatial qualities, sometimes to the detrimentof other cues. However with some notable and recent exceptions, computer visionsystems treat cast shadows not as signal but as noise. This paper provides a conciseyet comprehensive review of the literature on cast shadow perception from across thecognitive sciences, including the theoretical information available, the perception ofshadows in human and machine vision, and the ways in which shadows can be used.Peer reviewe

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This paper presents a novel approach to the detection of unusual or interesting events in videos involving certain types of intentional behaviour, such as pedestrian scenes. The approach is not based upon a statistical measure of typicality, but upon building an understanding of the way people navigate towards a goal. The activity of agents moving around within the scene is evaluated based upon whether the behaviour in question is consistent with a simple model of goal-directed behaviour and a model of those goals and obstacles known to be in the scene. The advantages of such an approach are multiple: it handles the presence of movable obstacles (for example, parked cars) with ease; trajectories which have never before been presented to the system can be classified as explicable; and the technique as a whole has a prima facie psychological plausibility. A system based upon these principles is demonstrated in two scenes: a car-park, and in a foyer scenario 1 .

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Figure 1: First 3 principal components of our statistical diffuse (left) and specular (middle) albedo models. Both are visualised in linear sRGB space. Right: rendering of the combined model under frontal illumination in nonlinear sRGB space.