Goniophotometry and assessment of bidirectional photometric properties of complex fenestration systems

This paper seeks to provide an overview of the currently available assessment tools for bidirectional transmission or reflection distribution functions (BTDFs and BRDFs) of complex fenestration systems (CFS). In the first part of the paper, the existing experimental devices (goniophotometers) developed specifically for CFS measurement are described. All but two are based on a scanning process to investigate the emerging light flux distribution, the alternative approach being based on digital imaging techniques. A critical analysis of their advantages and shortcomings is proposed to provide both researchers interested in replicating them and more generally potential users of BTDF or BRDF data with a lucid idea of the available options.