Imaging acquisition and mapping for fast directional reflectance measurements
We present an alternative measurement method for BRDF characterization. It is based on imaging instead of angular sampling. Under illumination, the reflectance characteristic of the analyzed material is projected onto a hemispheric diffuse reflective dome surrounding the probe. Images of the dome are taken to capture the directional distribution of the reflected light. This shows the main advantage of the new method: The simultaneous capture of the reflectance within a hemispherical sector, therefore accelerating greatly the data acquisition. However, some additional processing steps have to be implemented to achieve results comparable to the sampling method. Captures with different integration times have to be merged into a high dynamic range (HDR) image and a pixel mapping to absolute scattering angles in spherical coordinates (elevation and azimuth) has to be registered. Measurements acquired with this first simple approach are quantitatively compared to the aforemen tioned established sampling acquisition method for two different materials: A diffuse lambertian reference and a higher gloss degree material. These results are discussed in the last section and will serve as guidelines for future iteration developments of the proposed method.