Purchase this article with an account.
Scott Mooney, Barton Anderson; Illusory transparency and optical blur induced by single shaded surfaces. Journal of Vision 2018;18(10):889. doi: 10.1167/18.10.889.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
A large body of research has investigated the visual system's ability to disentangle 3D surface shape, material, and illumination from ambiguous image gradients, but less is known about how surface features are distinguished from optical defocus. Defocused surfaces can generate gradients that closely resemble the low spatial frequency shading patterns generated by fully focused, smoothly curved matte surfaces. We previously showed that the visual system misinterprets fully focused shaded surfaces as blurred in the absence of sharp bounding contours. Here, we report a surprising new form of illusory transparency induced by coherent, rendered surfaces. When low frequency surface relief and high frequency surface relief are combined into a single surface, they appear as two distinct layers, and the low frequency component continues to appear blurred. We sought to determine what form of texture is needed to generate a percept of a coherent, single surface and eliminate this illusory blur. We synthesized stochastic surface relief such that it would produce images with a 1/f amplitude spectrum, then introduced a 'gap' of varying width in the middle bands of frequencies used to construct the surface's texture. When the gap was sufficiently large, the low and high frequency components appeared to split into two superimposed layers. The perception of a coherent surface was lost when the gap's bandwidth was greater than approximately one octave, consistent with experiments using simple luminance gratings (Stromeyer & Klein, 1975). These results suggest that discontinuous gradients in the frequency domain are experienced as two distinct generative sources, even when produced by a single realistic surface. Our findings further demonstrate that the illusory blur induced by low frequency shaded surfaces can only be eliminated with textures that produce images exhibiting a continuous band of frequencies, which reflects the self-similar structure of the fractal textures that populate our natural environment.
Meeting abstract presented at VSS 2018
This PDF is available to Subscribers Only