1. A method, comprising: detecting one or more objects for a full range of one or more attributes at each location of an image; generating a set of positional constraints indicating an expected range of values for each position in said image for one or more of said attributes based on said detected objects, wherein said generating step employs a geometric model of a scene in said image to generate said set of positional constraints and wherein said expected range of values for at least one position in said image is inferred based on one or more other positions in said image; and detecting one or more objects in said image using said expected range of values for each position in said image for said one or more of said attributes.