Giachetti, AndreaCiortan, Irina MihaelaDaffara, ClaudiaPintus, RuggeroGobbetti, EnricoTobias Schreck and Tim Weyrich and Robert Sablatnig and Benjamin Stular2017-09-272017-09-272017978-3-03868-037-62312-6124https://doi.org/10.2312/gch.20171288https://diglib.eg.org:443/handle/10.2312/gch20171288We propose a novel multi-spectral reflectance transformation imaging (MS-RTI) framework for the acquisition and direct analysis of the reflectance behavior of heterogeneous artworks. Starting from free-form acquisitions, we compute per-pixel calibrated multi-spectral appearance profiles, which associate a reflectance value to each sampled light direction and frequency. Visualization, relighting, and feature extraction is performed directly on appearance profile data, applying scattered data interpolation based on Radial Basis Functions to estimate per-pixel reflectance from novel lighting directions. We demonstrate how the proposed solution can convey more insights on the object materials and geometric details compared to classical multi-light methods that rely on low-frequency analytical model fitting eventually mixed with a separate handling of high-frequency components, hence requiring constraining priors on material behavior. The flexibility of our approach is illustrated on two heterogeneous case studies, a painting and a dark shiny metallic sculpture, that showcase feature extraction, visualization, and analysis of high-frequency properties of artworks using multi-light, multi-spectral (Visible, UV and IR) acquisitions.I.4.1 [Image processing and Computer Vision]Digitization and Image CaptureImaging GeometryI.3.3 [Computer Graphics]Digitizing and Scanning—I.3.8 [Computer Graphics]Applications10.2312/gch.2017128819-28