Exploring the role of caustics in translucency perception — An eye tracking approach

Abstract

Translucency is an important appearance attribute. The caustic patterns that are cast by translucent objects onto another surface encapsulate information about subsurface light transport properties of a material. A previous study demonstrated that objects placed on a white surface are considered more translucent by human observers than identical objects placed on a black surface. The authors propose the lack of caustics as a potential explanation for these discrepancies — since a perfectly black surface, unlike its white counterpart, does not permit observation of the caustics. We hypothesize that caustics are salient image cues to perceived translucency, and they attract the visual attention of the human observers when assessing translucency of an object. To test this hypothesis, we replicated the experiment reported in the previous study, but in addition to collecting the observer responses, we also conducted eye tracking during the experiment. This study has revealed that although gaze fixation patterns differ between white and black floor images, the objects’ body still attract most of the fixations, while caustics might be a cue of only secondary importance.