The role of color in the perception of three-dimensional shape

Phillip J Marlow,Karl R Gegenfurtner,Barton L Anderson

doi:10.1016/j.cub.2022.01.026

Phillip J Marlow, Karl R Gegenfurtner + Show 1 more

Open Access

https://doi.org/10.1016/j.cub.2022.01.026

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Abstract

SummaryThe human visual system can derive information about three-dimensional (3D) shape from the structure of light reflected by surfaces. Most research on single static images has focused on the 3D shape information contained in variations of brightness caused by interactions between the illumination and local surface orientation (“shading”).1, 2, 3, 4, 5, 6 Although color can enhance the recovery of surface shading when color and brightness vary independently,7, 8, 9 there is no evidence that color alone provides any information about 3D shape. Here, we show that the wavelength-dependent reflectance of chromatic materials provides information about the 3D shape of translucent materials. We show that different wavelengths of light undergo varying degrees of subsurface light transport, which generates multiple forms of spatial structure: wavelengths that are weakly reflected generate shading-like image structure, linked to 3D surface orientation, whereas wavelengths that penetrate more deeply into the material are primarily constrained by the direction of surface curvature (convexities and concavities).10 Psychophysical experiments demonstrate that the enhanced perception of 3D shape in chromatic translucent surfaces arises from the shading structure generated by weakly reflected wavelengths, which, in turn, generates correlated spatial variations in saturation. These results demonstrate a new functional role for color in the perception of the 3D shape of translucent materials.

Highlights

Materials differ in how permeable they are to light
Chromatic materials are experienced as having specific hues, lightnesses, and saturations, which depend on the proportions of different wavelengths a material emits
The amount of light striking a given point on a surface depends on its local orientation relative to the direction of illumination, which generates the patterns of surface shading: the amount of light returned from a point is a fixed proportion of the amount of incident light.[1]

Summary

Introduction

Materials differ in how permeable they are to light. Light penetrating ‘‘opaque’’ materials is only transported within their superficial layers, where it is scattered and re-emerges close to where it entered. The amount of light striking a given point on a surface depends on its local orientation relative to the direction of illumination, which generates the patterns of surface shading: the amount of light returned from a point is a fixed proportion of the amount of incident light.[1] For diffuse, uniformly colored surfaces, the proportion of light reflected in each wavelength band is fixed. The same pattern of shading is generated by all wavelength bands, differing only by a multiplicative scale factor (Figures 1B and 1C)

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