A Psychophysical Analysis of Fabricated Anisotropic Appearance

Abstract

Many materials change surface appearance when observed for fixed viewing and lighting directions while rotating around its normal. Such distinct anisotropic behavior manifests itself as changes in textural color and intensity. These effects are due to structural elements introducing azimuthally-dependent behavior. However, each material and finishing technique has its unique anisotropic properties which are often difficult to control. To avoid this problem, we study controlled anisotropic appearance introduced by means of 3D printing. Our work tends to link perception of directionality with perception of anisotropic reflectance effect it causes. We simulate two types of structure-based anisotropic effects, which are related to directional principles found in real-world materials. For each type, we create a set of test surfaces by controlling the printed anisotropy level and assess them in a psychophysical study to identify a perceptual scale of anisotropy. The generality of these scales is then verified by means of anisotropic surfaces appearance capturing using bidirectional texture function and its analysis on 3D objects. Eventually, we relate the perceptual scale of anisotropy to a computational feature obtained directly from anisotropic highlights observed in the captured reflectance data. The feature is validated using a psychophysical study analyzing visibility of anisotropic reflectance effects.