Infer light diffuseness on light probes with different kinds of mesoreliefs

The appearance of objects varies enormously depending on light diffuseness. Conversely, the appearance of objects might be a cue to the light diffuseness. This would provide a solution for lighting designers to guess-estimate the light diffuseness levels based on the appearance of a light probe. However, the question remains whether rough probe provides additional cues about light diffuseness comparing with the smooth probes. If the answer to the last question is yes, whether different kinds of roughness performs the same. Furthermore, how the estimation of light diffuseness might be influenced by the illumination directions. To answer these questions, an appearance-matching experiment was performed, within which white spherical probes with four kinds of surface mesoreliefs were adopted and 5 illumination directions were tested. The results confirmed that observers’ abilities to match the light diffuseness were improved by the use of probes with 3D texture, which means that observers can derive light diffuseness from the additional cues provided by the texture over the rough probe. However, the results showed that the roughness has no obvious effect on diffuseness perception at illumination direction of 90° or 120° owing to the much useful information provided by the terminator of the body shadow.