On the Influence of Dynamic Illumination in the Perception of Translucency

Translucent materials are ubiquitous in our daily lives, from organic materials such as food, liquids or human skin, to synthetic materials like plastic or rubber. In these materials, light penetrates inside the surface and scatters in the medium before leaving it. While the physical phenomena responsible for translucent appearance are well known, understanding how human observers perceive this type of materials is still an open problem: The appearance of translucent objects is affected by many dimensions beyond the optical properties of the material, including shape and illumination. In this work, we focus on the effect of illumination on the appearance of translucent materials. In particular, we analyze how static and dynamic illumination impact the perception of translucency. Previous studies have shown that changing the illumination conditions results in a constancy failure, specially in media with anisotropic phase functions. We extend this line of work, and analyze whether motion can alleviate such constancy failure. To do that, we run a psychophysical experiment where users need to match the optical density of a reference translucent object under both dynamic and static illumination. Surprisingly, our results suggest that in most cases light motion does not impact the perceived density of the translucent material. Our findings can have implications for material design in predictive rendering and authoring applications.