Many real-world materials exhibit significant changes in appearance when rotated along a surface normal. The presence of this behavior is often referred to as visual anisotropy. Anisotropic appearance of spatially homogeneous materials is commonly characterized by a four-dimensional BRDF. Unfortunately, due to simplicity most past research has been devoted to three dimensional isotropic BRDFs. In this paper, we introduce an innovative, fast, and inexpensive image-based approach to detect the extent of anisotropy, its main axes and width of corresponding anisotropic highlights. The method does not rely on any moving parts and uses only an off-the-shelf ellipsoidal reflector with a compact camera. We analyze our findings with a material microgeometry scan, and present how results correspond to the microstructure of individual threads in a particular fabric. We show that knowledge of a material’s anisotropic behavior can be effectively used in order to design a material-dependent sampling pattern so as the material’s BRDF could be measured much more precisely in the same amount of time using a common gonioreflectometer.

Date Published: 13 March 2015
PDF: 10 pages
Proc. SPIE 9398, Measuring, Modeling, and Reproducing Material Appearance 2015, 93980P (13 March 2015); doi: 10.1117/12.2078361

Published in SPIE Proceedings Vol. 9398:
Measuring, Modeling, and Reproducing Material Appearance 2015
Maria V. Ortiz Segovia; Philipp Urban; Francisco H. Imai, Editor(s)