Reconstruction of Spectra Using Empirical Basis Functions

Physically-based image synthesis requires measured spectral quantities for illuminants and reflectances as part of the virtual scene description to compute trustworthy lighting simulations. When spectral distributions are not available, a method to reconstruct spectra from color triplets needs to be applied. A comprehensive evaluation of the practical applicability of previously published approaches in the context of realistic rendering is still lacking. Thus, we designed three different comparison scenarios typical for computer graphic applications to evaluate the suitability of the methods to reconstruct illumination and reflectance spectra. Furthermore, we propose a novel approach applying empirical mean spectra as basis functions to reconstruct spectral distributions. The mean spectra are derived from averaging sets of typical red, green, and blue spectra. This method is intuitive, computationally inexpensive, and achieved the best results for all scenarios in our evaluation. However, reconstructed spectra are not unrestrictedly applicable in physically-based rendering where reliable synthetic images are crucial.