Journal of Vision (2020) 20(4):13, 1–18 1 Effects of light map orientation and shape on the visual perception of canonical materials Fan Zhang Perceptual Intelligence Lab, Faculty of Industrial Design Engineering, Delft University of Technology, Delft, The Netherlands Huib de Ridder Perceptual Intelligence Lab, Faculty of Industrial Design Engineering, Delft University of Technology, Delft, The Netherlands Pascal Barla INRIA, University of Bordeaux, Bordeaux, France Sylvia Pont Perceptual Intelligence Lab, Faculty of Industrial Design Engineering, Delft University of Technology, Delft, The Netherlands We previously presented a systematic optics-based canonical approach to test material-lighting interactions in their full natural ecology, combining canonical material and lighting modes. Analyzing the power of the spherical harmonics components of the lighting allowed us to predict the lighting effects on material perception for generic natural illumination environments. To further understand how material properties can be brought out or communicated visually, in the current study, we tested whether and how light map orientation and shape affect these interactions in a rating experiment: For combinations of four materials, three shapes, and three light maps, we rotated the light maps in 15 different configurations. For the velvety objects, there were main and interaction effects of lighting and light map orientation. The velvety ratings decreased when the main light source was coming from the back of the objects. For the specular objects, there were main and interaction effects of lighting and shape. The specular ratings increased when the environment in the specular reflections was clearly visible in the stimuli. For the glittery objects, there were main and interaction effects of shape and light map orientation. The glittery ratings correlated with the coverage of the glitter reflections as the shape and light map orientation varied. For the matte objects, results were robust across all conditions. Last, we propose combining the canonical modes approach with so-called importance maps to analyze the appearance features of the proximal stimulus, the image, in contradistinction to the physical parameters as an approach for optimization of material communication. Introduction One of the aims of material perception research is to understand how human beings perceive materials in varying lighting environments. The endless combinations of materials and lighting environments pose a difcult challenge on this matter in two important ways, namely, (a) same material under diferent lights and belonging to diferent shapes can have a diferent appearance, and (b) same appearance can be the result of diferent combinations of lightings, shapes, and materials (image ambiguities). The appearance of materials varies enormously depending on the lighting and shape (Olkkonen & Brainard, 2010), and human observers were found not to be “material constant” if the shape (Nishida & Shinya, 1998; Vangorp, Laurijssen, & Dutré, 2007) or the lighting varies (Dror, Willsky, & Adelson, 2004; Pont & te Pas, 2006). A well-known lighting efect for glossy surfaces that has been found in many studies is that glossy surfaces are perceived as rather matte under very difuse lighting and glossier under directed lighting (Dror, Willsky, & Adelson, 2004; Pont & te Pas, 2006; Zhang, de Ridder, Fleming, & Pont, 2016; Zhang, de Ridder, & Pont, 2015, 2018) or perceived to have diferent levels of glossiness under diferent artifcial or natural lighting environments (Adams et al., 2018; Doerschner, Boyaci & Maloney, 2010; Fleming, Dror, & Adelson, 2003; Olkkonen & Brainard, 2010; Motoyoshi & Matoba, 2012; Wendt & Faul, 2017; Zhang, de Ridder, Barla, & Pont, 2019). In a recent study on textiles, the textiles Citation: Zhang, F., de Ridder, H., Barla, P., & Pont, S. (2020). Effects of light map orientation and shape on the visual perception of canonical materials. Journal of Vision, 20(4):13, 1–18, https://doi.org/10.1167/jov.20.4.13. https://doi.org/10.1167/jov.20.4.13 Received December 28, 2018; published April 23, 2020 ISSN 1534-7362 Copyright 2020 The Authors This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License. Downloaded from jov.arvojournals.org on 07/24/2020