How direct light and diffusive light influence the appearance of objects?

Abstract

Shape, texture and light are crucial factors to determine the appearance of object. Recently, lighting environment has become diversified due to the improvement of lighting technology and it is important to consider the appearance of objects under various lighting conditions. Our previous study showed that the diffuseness of lighting influenced the perceived glossiness and roughness of an object (ICVS2017). In this study, we investigate the influence of direct light and diffusive light to the appearance of surface properties of an object. A miniature room was illuminated by a mixed lighting with directional light and diffusive light We used two LED lamps and a diffuser board. One was far from the diffuser board, giving a diffusive lighting condition. The other was close to the diffuser boards, giving a direct lighting condition. We tested five lighting conditions by changing the intensity ratio of each lamp. The test samples were made with a 3D printer. We used glossy and matte square samples with sine-wave surface which depth were 1.0 and 0.5 mm and three types of frequencies. Observers adapted to the illumination of the miniature room for one minute, and then responded the roughness and glossiness of the test samples using a magnitude estimation method. As a result, samples tended to appear less glossy and smoother as the lighting became more diffusive. Perceived glossiness showed clearer influence of lighting conditions for glossy and high-frequency-surface samples. Perceived roughness showed clearer influence of lighting conditions for matte surface samples.