Data and code for "Characterisation of material optical properties for indoor daylight simulation"

This repository contains the data and code for the PhD thesis chapter <strong>"Characterisation of material optical properties for indoor daylight simulation."</strong><strong>Summary:</strong> This chapter evaluates three image-based techniques for on-site material reflectance characterisation in daylight simulations—Illuminance-Proxy, Ferwerda’s phone-based method, and Luo’s learned SVBRDF estimation—and validates a spectral uplifting approach for non-visual simulations. A meeting room with diverse finishes was measured using a Konica Minolta CM-26dG spectrophotometer (SCI/SCE) to establish ground truth. The Illuminance-Proxy reconstructs wall reflectance maps from HDR luminance and sparse reference points (kriging); Ferwerda’s technique estimates tristimulus reflectance from unconstrained phone images; Luo’s technique infers diffuse/specular/roughness from flash-lit phone photos. Accuracy is reported using NMBE, NRMSE, ∆Eₐᵦ, and room-scale metrics (TAI, UDI, DGP). Ferwerda’s technique shows the most balanced performance (NMBE ≈ 13%, NRMSE ≈ 31%), stable across lighting conditions, with TAI overestimation of 33–65%. Illuminance-Proxy yields NMBE ≈ 19%, NRMSE ≈ 41%, but overpredicts TAI by ∼101% in the case study; a 3-channel HDR test indicates per-point ∆ρ &lt; 0.08. Luo’s technique exhibits the largest errors (NMBE ≈ 25%, NRMSE ≈ 62%), with ∆Eₐᵦ up to ∼60 and TAI overestimation up to ∼134%. All techniques predict low DGP with negligible deviation (NRMSE &lt; 0.02). Spectral uplifting reconstructs smooth, energy-conserving spectra with wavelength-wise errors typically &lt; 20%, yielding melanopic equivalent illuminance (EML) differences &lt; 6%. Overall, Ferwerda’s technique offers the best accuracy–practicability trade-off, Illuminance-Proxy is useful for planar diffuse surfaces when sparse ground truth is available, and spectral uplifting enables non-visual analyses from tristimulus inputs with minimal error.