IMPACT OF SURFACE CURVATURE ON SPECTRAL BRDF OF EFFECT COATINGS (PO15, Pages 295-302)

We applied the same effect coating with metallic pigments to three surfaces with different convex curvatures (flat, slightly curved and very curved), and their spectral BRDF was measured at different pairs of illumination and observation directions. We found that, at specular directions, the higher the curvature of the sample the lower the spectrally-averaged BRDF, whereas, at aspecular angles close to the specular directions, the higher the curvature the higher the spectrally-averaged BRDF, which is very likely due to the convolution by curvature. But, in addition, we have found another impact of the curvature, which is not spectrally neutral and cannot be explained by simple convolution. It is observed at some in-plane geometries with high incidence angles. The colour of the curved sample is slightly more chromatic at these geometries, which points out that the effect pigments contribute in higher extent to the spectral BRDF.