Fig. 13
From: Appearance-based evaluation of varnish removal methods in gilded surfaces
Biplot of the PCA for the first two PCs, calculated using the coefficients obtained for the BRDF model in the CIE Y coordinates (\(\alpha\), \(k_s\), and \(R_d\)) and gloss attributes (c and d). Oil gilding samples are displayed in orange (round markers), and water gilding samples are displayed in blue (triangle markers). PC1 and PC2 are representative of c and d respectively. Surfaces are clustered depending on their varnish level (reference or no varnish, varnished, and cleaned)