Physics and Measurement of Properties Linked to Appearance

Abstract

The measurement of the appearance of objects as perceived by individuals is necessary to meet industrial needs (quality control at the end of the production line, realistic reproduction of a 3D object, generation of new visual effects) and societal needs (development of virtual reality, creation of digital twins of cultural heritage objects). This need for measurement, initially addressed by colorimetry, has become more complex over the past 20 years with the arrival of new effects such as "sparkle" in the automotive industry, iridescence in cosmetics, and new demands such as measuring translucency for 3D printing or satin finish for natural-looking objects. To characterize these new effects, traditional measurement techniques have naturally evolved toward bidirectional quantities such as BRDF, BTDF, SVBRDF, or BSSRDF! Metrologists have developed instruments capable of measuring these new quantities. Today, there are solutions for acquiring them all, using rotation platforms, robotic arms, HDR imaging sensors, and very bright LED sources.