Looking against the light: How perception of translucency depends on lighting direction

Abstract

Translucency is an important aspect of material appearance. To some extent, humans are able to estimate translucency in a consistent way across different shapes and lighting conditions, i.e., to exhibit translucency constancy. However, Fleming and Bülthoff (2005) have shown that that there can be large failures of constancy, with lighting direction playing an important role. In this paper, we explore the interaction of shape, illumination, and degree of translucency constancy more deeply by including in our analysis the variations in translucent appearance that are induced by the shape of the scattering phase function. This is an aspect of translucency that has been largely neglected. We used appearance matching to measure how perceived translucency depends on both lighting and phase function. The stimuli were rendered scenes that contained a figurine and the lighting direction was represented by spherical harmonic basis function. Observers adjusted the density of a figurine under one lighting condition to match the material property of a target figurine under another lighting condition. Across the trials, we varied both the lighting direction and the phase function of the target. The phase functions were sampled from a 2D space proposed by Gkioulekas et al. (2013) to span an important range of translucent appearance. We find the degree of translucency constancy depends strongly on the phase function's location in the same 2D space, suggesting that the space captures useful information about different types of translucency. We also find that the geometry of an object is important. We compare the case of a torus, which has a simple smooth shape, with that of the figurine, which has more complex geometric features. The complex shape shows a greater range of apparent translucencies and a higher degree of constancy failure. In summary, humans show significant failures of translucency constancy across changes in lighting direction, but the effect depends both on the shape complexity and the translucency phase function.

Effect of Geometric Sharpness on Translucent Material Perception

“…In recent years, there has been significant progress in developing rendering algorithms and representations that, by modeling the underlying physics, can create realistic reproductions of translucency (Jensen, Marschner, Levoy, & Hanrahan, 2001; Donner & Jensen, 2008; Gkioulekas et al, 2013). As with physics, there have likewise been previous efforts trying to decipher the other major aspect of translucent appearance, namely its perception by the human visual system (Fleming & Bülthoff, 2005; Motoyoshi, 2010; Anderson, 2011; Nagai et al, 2013; Gkioulekas et al, 2013; Xiao et al, 2014; Chowdhury, Marlow, & Kim, 2017; Marlow, Kim, & Anderson, 2017). Despite this, our understanding of translucency perception remains limited.…”

“…The study of the perception of translucency is confounded by the fact that there exists a tight coupling between how humans perceive the illumination, shape, and material properties of translucent objects (Xiao et al, 2014; Marlow et al, 2017). Recently, Chowdhury et al (Chowdhury et al, 2017) showed that the perception of the 3D shape of a translucent object is different from that of an opaque one.…”

Estimating mechanical properties of cloth from videos using dense motion trajectories: human psychophysics and machine learning

“…For example, to grasp a sweater, it is helpful to know its heaviness and stretchability before we come into contact with it. Previous work in material perception has mainly focused on understanding the optical properties of rigid objects, such as the surface gloss and translucency (Fleming, Dror, & Adelson, 2003;Fleming & Bülthoff, 2005;Landy, 2007;Motoyoshi, Nishida, Sharan, & Adelson, 2007;Ho, Landy, & Maloney, 2008;Xiao & Brainard, 2008;Kim & Anderson, 2010;Wijntjes & Pont, 2010;Motoyoshi, 2010;Doerschner et al, 2011;Fleming, Jäkel, & Maloney, 2011;Gkioulekas et al, 2013;Xiao et al, 2014). But many materials around us are soft and deformable (e.g., cloth, gels, and liquids).…”

Material category of visual objects computed from specular image structure

“…A potential reason for this is that a material's surface reflectance properties create some of its most salient optical characteristics and relying on such characteristics could carry ecological importance when other cues to material are not available. For instance, the visual effects of translucency can be greatly diminished with frontal lighting (Xiao et al, 2014); in such cases, image features caused by specular reflections might remain diagnostic of translucent materials (e.g. porcelain).…”