The measurement of hyperspectral bidirectional reflectance distribution function (BRDF) of a material is a key issue in physically based spectral rendering. We present here a device for measuring BRDF, enabling high spectral sampling (sub-nanometric from 450 nm to 1100 nm) with the counterpart of sparser angular sampling. To overcome this problem, we propose an interpolation method that respects the physical and topological properties of the BRDF by construction. The characteristic properties of the material deduced from the interpolated data set correspond to the reference values obtained using dedicated measuring instruments.