Sammendrag
Colour alone is not sufficient to communicate and reproduce how objects and materials look. While colours are usually measured locally, for a spot, real-life objects are characterized by spatially and temporally varying colour. The regularities of spatio-temporal variation of colour provide information about specular reflection of light, transmission of light through subsurface, and spatial variation of surface reflectance and geometry. These types of spatio-temporal variation of colour are described by gloss, translucency, and texture, respectively – and along with colour constitute what is usually called basic appearance attributes. While perception and reproduction of colour are relatively well-understood, the research on perception of other basic appearance attributes is in its infancy. Little is known about the physiological mechanisms of gloss, translucency and texture perception, both on the retinal, as well as cortical level. No standard observer is defined and no robust appearance models exist for those attributes. This has a considerable implication for current colour technologies. While an immense amount of work has been done for accurate cross-media colour reproduction, the generation of the desired look of complex, real-life objects requires reproduction of gloss, translucency, and texture as well. For instance, for a 3D printed prosthesis of a human limb to look realistic, not only colour, but also gloss, translucency, and texture should match with those of real human skin. This chapter summarizes the knowledge status on the perception of gloss and translucency by the human visual system, identifies current challenges, and discusses the implications they have for future colour imaging and manufacturing technologies. Analysis of texture perception is beyond the scope of this chapter.
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