Bidirectional Reflectance Definitions

The Joint Research Project „Bidirectional Reflectance Definitions“  focuses on the pre-normative work required to clarify how measurements on standard materials and surfaces exhibiting goniochromatism, gloss and sparkle visual effects should be carried out. This will enable a reliable comparison of results provided by different measurement devices and better control of the visual effects of products.

In this field, the relevant radiometric quantity is the Bidirectional Reflectance Distribution Function (BRDF), which contains extensive information about the light reflected by a surface and therefore information on the appearance of a product.
Significant metrological effort on BRDF measurements has been made over recent years, particularly at the European level due to the EMRP project IND52 xDReflect.

Current standards on colour measurement (ISO 11664) and gloss measurement (ISO 2813) are not adapted to the characterisation of sophisticated visual effects and no standard exists for BRDF  or sparkle.

The main objectives of this project are:

  • Guidance on BRDF measurement and how to sample the BRDF space will be made available to CIE TC2-85, as a first step to standardise BRDF measurements.
  • A universal BRDF data format will be developer
  • Propose a new method for gloss measurement that correlates with visual perception
  • Propose a consensual definition of sparkle and graininess measurands and to define procedures for their measurement in correlation with visual scales for sparkle and graininess

All normative works are going on board of International Commission on Illumination (CIE) in the following CIE Technical Committees:

This project challenges following four out of ten CIE Research Topics:

Outputs of the BiRD project will be used in the recently started Joint Research Project  “New quantities for the measurement of appearance“.   The project will involve defining the new quantities Bidirectional Transmittance Distribution Function (BTDF) and Bidirectional Surface Scattering Reflectance Distribution Function (BSSRDF), and further improving the measurements of Bidirectional Reflectance Distribution Function (BRDF). For more  information, please visit the project website https://bxdiff.cmi.cz/.