Gloss averaging and simultaneous contrast effects on real bicolored glossy surfaces

Whether a surface is glossy or matte is physically independent of whether it is light or dark. Perceptually however, the albedo of specularly or diffusely reflecting surfaces can strongly influence perceived gloss (Pellacini et al., 2000, Proceedings of SIGGRAPH). Here we ask whether glossiness judgments are more constrained if there are variations of albedo within a single surface. To investigate the influence of different albedos on a single surface we first created a set of 45 real surfaces. Based on a 3D model, molds were cut out of polymer foam by the use of a CNC (Computerized Numerical Control) machine. Sheets of plastic (350mm x 350mm) were heated up inside a vacuum forming machine and then stretched onto the mold and later spray-painted in five colors and five gloss levels. Additionally, we also painted surfaces with combinations of two colors next to each other. 11 participants looked at each surface in a light box, through a viewing hole, and they were encouraged to rate the gloss on a scale from one to seven. In a second experiment participants rated only the left or the right half of each bi-colored surface. Our results confirm that perceived gloss varies with albedo. In addition, perceived global gloss of bicolored surfaces were close to the ratings of unicolored surfaces whose albedos are the average of the bicolored surfaces. However, results from the second experiment indicate that when participants rate gloss only on one side of the surface, judgments for lighter colors show simultaneous gloss contrast effects of the darker colors next to it. In conclusion we propose a fairly easy method to create mathematically defined bumpy, plastic surfaces with various colors and gloss levels. Our results from multi-colored surfaces show both averaging and simultaneous gloss contrast effects depending on the task.

Meeting abstract presented at VSS 2015