The Impact of Optical and Geometrical Thickness on Perceived Translucency Differences

In this work we study the perception of suprathreshold translucency differences to expand the knowledge about material appearance perception in imaging and computer graphics, and 3D printing applications. Translucency is one of the most considerable appearance attributes that significantly affects the look of objects and materials. However, the knowledge about translucency perception remains limited. Even less is known about the perception of translucency differences between materials. We hypothesize that humans are more sensitive to small changes in absorption and scattering coefficients when optically thin materials are examined and when objects have geometrically thin parts. To test these hypotheses, we generated images of objects with different shapes and subsurface scattering properties and conducted psychophysical experiments with these visual stimuli. The analysis of the experimental data supports these hypotheses and based on post experiment comments made by the observers, we argue that the results could be a demonstration of a fundamental difference between translucency perception mechanisms in see-through and non-see-through objects and materials.