New quantities for the measurement of appearance

Appearance is increasing used as a differentiator in product quality and desirability. Previously accepted references, such as reflectance at single angular measurements, are becoming obsolete as branding depends on more complex appearance factors. Bidirectional Transmittance Distribution Function (BTDF) and Bidirectional scattering distribution function (BSSRDF) are computer graphics algorithms that describe visual effects caused by surfaces. Commercial bidirectional spectrophotometers are available for which NMIs could provide calibration services, although there’s no standard definitions for these quantities.

The project will define BTDF and BSSRDF, develop primary facilities for their realisation traceable to the SI, and improve measurements of the Bidirectional Reflectance Distribution Function (BRDF). New calibration services will arise for spectrophotometers manufacturers and the industrial R&D market. A definition and realisation of BSSRDF will provide the first calibration solution, impacting industries such as cosmetics, automotive, plastics, and paper, as well as the rendering software market.

New metrological references for spectrophotometry will improve product quality control and virtual product representation in digital design.