Estimating Spectral BRDF Parameters Using Handheld Devices

The Bidirectional Reflectance Distribution Function (BRDF) is one of the tools for characterising the appearance of real-world materials. However, bidirectional reflectance measurements and data processing can be time-consuming and challenging. This paper aims to estimate the BRDF values of eight matt samples using two portable, handheld devices, one for diffuse reflectance and one for specular reflectance measurements. The data is fitted to the Cook-Torrance BRDF model in the spectral domain to get the optimised parameters and the estimated spectral BRDF values using three different cost functions. The estimated BRDF is evaluated using a colour-difference metric. The results show that it would be possible to estimate spectral BRDF of a sample using measurements from two simple measurement devices having fewer angle combinations for both the diffuse and specular measurements. This results in a shorter measurement and processing time, lower storage usage, and estimations of spectral BRDF values. Moreover, the cube root cosine-weighted RMSE cost function shows more consistency in the colour reproduction estimated by the fitted BRDF model.