Reflection symmetry drawing8/12/2023 The extreme case of this surface signature is seen in the extended highlights that run along the cylindrical portions of a reflective shape, a feature that was the first to be used by artists to capture surface curvature with reflections (see Gombrich, 1976, for his extraordinary analysis of the use of this cue by Greek painters). (2004) point out that reflections are compressed along the axis of maximum curvature and that this produces a signature of the surface shape over wide changes in the scene being reflected. (2003) showed that reflections need to have the statistics of real world scenes, including specifically some edges and bright light sources, but otherwise they do not have to match the objects that should actually be present for the reflecting surface to appear shiny. A survey of medieval, Flemish, and modern paintings reveals any number of extraneous items in reflections that should not be there or items that are absent when they should be present. ![]() Despite this obvious impossibility, almost anything can be put in the reflection as long as it is bright and curves appropriately for the reflecting surface curvature. Highly curved, reflective surfaces are the mirror equivalent of a fish-eye lens so much of the scene in front of the object is captured in the reflection and, optically, that should also include the scene around the observer outside of the picture space. The evidence from mimicry and the success of highlights in painting suggests that the analysis of highlights may be deeply embedded in our visual systems, as well as those of other species.īeginning with the Greeks and Romans, artists have exploited highlights to add depth and realism to their paintings (see Miller, 1998, for a remarkable tour of reflections in art). When we consider reflections, it is helpful to divide them into two types: highlights on curved, glassy surfaces, and extended reflections on flat reflecting surfaces. In this article we explore the perception of reflection by studying artists’ techniques for representing reflections in particular, we are interested in what works despite deviations from the rules of optics ( Cavanagh, 2005). This example demonstrates that we can understand a great deal about the rules used by our visual system by identifying the inaccuracies of depiction, whether by animals or by painters, that we do not notice. Of course, the highlight also fools us - if we move our heads, the white spot does not lose its reflective quality. For the predator, the mimicked highlight must be conveying the additional realism of a reflection, and its immobility must not be breaking any of the rules for reflections actually implemented in the predator's visual system. Clearly, the fake highlight does work or it would not have survived eons of selection pressure. Any visual system that interpreted reflections based on the rules of optics would immediately notice that the mimicked highlight was not optically correct and that would be it for the prey. True reflections from a curved surface move as the observer moves, but of course, the pigment on the mimicked highlight cannot. ![]() Here we get a free insight into the visual system of the predators for the species that use highlights. In many cases, these eyespots incorporate a white highlight ( Fig. Snakes, frogs, fish, and most notably moths and butterflies often evolve eyespots to disorient predators. The highlights from eyes are salient enough to be incorporated into the eyespots often seen in animal mimicry. Reflections are not uncommon in natural scenes but until the development of mirrors, reflecting surfaces were limited to just a few materials such as still water, glassy minerals, and, of course, eyes.
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