On the visual appearance of objects

Abstract

When looking around in the world, humans have to figure out what it is they see, what the shapes of things are, what kinds of materials they are made of, and what their potential uses or dangers are. In addition to meaning, aesthetic value or affordance, the visual system also extracts some more fundamental object properties. The position, that perceived object shape is determined exclusively by the objects’ physical shape, is therefore clearly untenable. Likewise, perceived material and perceived illumination characteristics are also not determined exclusively by their respective physical counterparts. The problem of what objects look like is certainly not a trivial problem. It determines whether people approach an object carefully or not, if and how they pick it up, etc. This chapter examines the difficulties that humans face when looking at the real world. It examines the perceived shape, material properties, and illumination of objects with special emphasis on the perceived shape. There are physical relationships between shape, material, and illumination once certain simple assumptions are made. This chapter provides the necessary theoretical background on the physical properties and relationships between shape, material, and illumination of objects in projection. It discusses the physical correlates for perceived object properties. It also discusses perceptual organization and whether perceived object properties conform to physical constraints, that is, whether they form a coherent set. In addition it discusses how additional cues can be used to form a coherent percept.