Effects of Shape, Roughness and Gloss on the Perceived Reflectance of Colored Surfaces

Abstract

This study examined perceptual differentiation of specular from diffuse shading for the recovery of surface color and gloss. In Experiment 1, we parametrically varied the mesoscale relief height of globally planar surfaces, specular sharpness and the orientation of the surface relative to the light source. We obtained psychophysical matches for perceived color saturation and value (HSV), but also considered whether the main effects could be influenced by color space used when transforming data to perceptually-uniform CIE LCH space. Results revealed strong interactions between perceived color attributes and the lighting conditions, the structure of specular reflections, and surface relief. Declines in saturation were observed with increasing specular roughness (using an HSV color representation), but no similar decline was observed in chroma (using a CIE LCH color representation). Experiment 2 found strong negative correlations between perceived gloss and specular roughness. Perceived gloss also depended on mesoscopic relief height and orientation of the surface relative to the light source. Declines in perceived gloss moderately accounted for the variability in color saturation and value matches obtained in Experiment 1. We found information about perceived specular coverage could further improve the model's accountability of perceived color saturation and lightness (Experiment 3). These findings together suggest that perceived color saturation and color value depends on the visual system's ability to distinguish the underlying diffuse shading from specular highlights in images.

Surface properties and the perception of color

“…The purpose of Experiment 1 was to extend the findings of the original Honson et al (2020) study to multiple hues. Honson et al (2020) found that there was large variation in perceived saturation and lightness as a function of changes in specular roughness, mesoscopic shape, and orientation of the planar surfaces to the light source—which can profoundly change the way light interacts with and is distributed across a surface. Specular coverage will be greater when orienting the surface at 45° so its normals bisect the angle formed between the illumination and viewing directions.…”

“…We measured perceived lightness and saturation ( Experiment 1 ), perceived gloss ( Experiment 2 ), and perceived specular coverage ( Experiment 3 ) for surfaces rendered across these hue conditions at different levels of relief height, specular roughness, and surface orientation relative to the light source. Given that the findings of Honson et al (2020) may be explained by the inability to disentangle specular content from diffuse shading, we predicted that differences in the pattern of results for perceived lightness and saturation would be observed for blue surfaces but would be similar for red and green surfaces. This difference may be predicted by perceptual biases that exist along the blue/yellow axis that make it difficult for the visual system to disentangle a blue surface hue from the illuminant ( Churma, 1994 ; Pearce et al, 2014 ; Winkler et al, 2015 ; Radonijić et al, 2016 ; Weiss et al, 2017 ; Aston et al, 2019 ).…”

“…In more recent work on surface properties, Honson, Huynh-Thu, Arnison, Monaghan, Isherwood, and Kim (2020) investigated how object shape, specularity, and surface orientation affect perceived color and gloss. To investigate these material properties, they manipulated the mesoscopic relief height, specular roughness, and orientation of surfaces relative to a primary overhead light source.…”

“…The majority of research on the blue/yellow perceptual bias has so far only used two-dimensional images to study this phenomenon and/or focused solely on measuring color constancy ( Churma, 1994 ; Pearce et al, 2014 ; Winkler et al, 2015 ). Although some studies investigating differences across hues have been conducted using real or rendered 3D objects ( Xiao & Brainard, 2008 ; Giesel & Gegenfurtner, 2010 ; Xiao et al, 2012 ; Granzier et al, 2014 ), it is unclear the extent to which glossiness and specular coverage (as investigated previously in Honson et al, 2020 ) could account for perceptual differences in saturation and lightness judgments across a wider range of surface and material properties (e.g., mesoscopic relief height, specular roughness, orientation to light source, hue).…”

“…To address this gap, here we further evaluated the findings of Honson et al (2020) by assessing whether the effects of gloss on perceived color saturation and lightness differ across a wider range of hues—red, green, and blue. We measured perceived lightness and saturation ( Experiment 1 ), perceived gloss ( Experiment 2 ), and perceived specular coverage ( Experiment 3 ) for surfaces rendered across these hue conditions at different levels of relief height, specular roughness, and surface orientation relative to the light source.…”