2/20/2023 0 Comments Speed movingimages transparent![]() To analyze the critical stimulus characteristics of this phenomenon, we tested three other conditions. 1 C), indicating that the impression of a transparent liquid was clear and compelling to them. The video clips received a very high score (4.48, “original video clip” condition in Fig. We presented these video clips to human observers and asked them to rate the strength of their transparent liquid impression on a five-point scale (1, no impression of a transparent liquid, to 5, vivid impression of a transparent liquid). In the resulting video clips, it looked as if a transparent liquid were flowing over a static background pattern. We eliminated specular reflections at the liquid surface to examine the pure effects of image deformation. Using Blender software, we rendered computer-graphics scenes ( Movie S1) simulating the flow of a transparent liquid with the refractive index of water (1.33), and created video clips, each of which consisted of 90 frames and lasted 3 s. We first explored whether human observers could see a transparent liquid solely from the image deformation of an underlying pattern. Results Seeing a Transparent Layer from a Pure Image Deformation. Our findings indicate that the brain perceptually infers the presence of transparent liquids from a rather simple analysis of low-level spatiotemporal statistics of dynamic image deformation, instead of cognitively judging it based on high-level knowledge about water. In addition, we found that a transparent liquid was perceived not only when we took the pattern of dynamic deformation from a real or physics-based computer simulation of water flow, but also when we synthesized the pattern of deformation from a random source, in which we only made the spatiotemporal frequency amplitude spectrum of the image deformation close to that of real dynamic water. We found that the transparent liquid perception requires not only a sequence of static deformations, but also low-level motion signals accompanied by dynamic deformation. We carried out a series of psychophysical experiments to reveal the visual processing underlying the perception of a transparent layer from dynamic image deformations. ![]() Our findings indicate that the brain can perceptually infer the presence of “invisible” transparent liquids by analyzing the spatiotemporal structure of dynamic image deformation, for which it uses a relatively simple computation that does not require high-level knowledge about the detailed physics of liquid deformation. Furthermore, a transparent liquid layer perceptually emerges even from a randomly generated dynamic image deformation as long as it is similar to real liquid deformations in its spatiotemporal frequency profile. Although previous studies have indicated that these image deformations, at least static ones, play little role in perceptual transparency, here we show that dynamic image deformations of the background pattern, which could be produced by light refraction on a moving liquid’s surface, can produce a vivid impression of a transparent liquid layer without the aid of any other visual cues as to the presence of a transparent layer. Our daily experiences with transparent materials of this kind suggest that an alternative potential cue of visual transparency is image deformations of a background pattern caused by light refraction. Critical image cues to perceptual transparency, studied extensively in the past, are changes in luminance or color that could be caused by light absorptions and reflections by the front layer, but such image changes may not be clearly visible when the front layer consists of a pure transparent material such as water. Human vision has a remarkable ability to perceive two layers at the same retinal locations, a transparent layer in front of a background surface.
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