Effects of Illumination on the Categorization of Shiny Materials

TL;DR

This study investigates how different lighting conditions affect the perception and categorization of shiny metallic and black materials, revealing that illumination patterns can cause confusions between these categories.

Contribution

It introduces a quantitative analysis linking HDRI lighting patterns to perceptual biases in material categorization, highlighting the influence of illumination on visual judgments.

Findings

Lighting patterns significantly influence material categorization.

Metal and shiny black materials are often confused under certain lighting conditions.

Spherical harmonic analysis can predict perceptual biases based on illumination.

Abstract

The present research was designed to examine how patterns of illumination influence the perceptual categorization of metal, shiny black, and shiny white materials. The stimuli depicted three possible objects that were illuminated by five possible HDRI light maps, which varied in their overall distributions of illuminant directions and intensities. The surfaces included a low roughness chrome material, a shiny black material, and a shiny white material with both diffuse and specular components. Observers rated each stimulus by adjusting four sliders to indicate their confidence that the depicted material was metal, shiny black, shiny white or something else, and these adjustments were constrained so that the sum of all four settings was always 100%. The results revealed that the metal and shiny black categories are easily confused. For example, metal materials with low intensity light maps or a narrow range of illuminant directions are often judged as shiny black, whereas shiny black materials with high intensity light maps or a wide range of illuminant directions are often judged as metal. A spherical harmonic analysis was performed on the different light maps in an effort to quantitatively predict how they would bias observers' judgments of metal and shiny black surfaces.