Shape-from-shading for matte and glossy objects

We wanted to find out whether the presence of specular highlights on the otherwise matte objects would make a difference to the perceived surface relief. Six different, globally convex objects were displayed on a computer screen. The depicted objects were either matte or glossy and were illuminated from one of the two different directions. Shape-from-shading was evaluated with two different paradigms. In Experiment 1 observers were asked to set a number of local surface attitude probes such that the probes looked as if they were tangent to the objects' surfaces. In Experiment 2, observers were instructed to make traces of the contours of the depicted objects in the horizontal and vertical planes. Although the two tasks target different aspects of the perceived surface, they give essentially similar results here. In both tasks we found differences that were induced by changing the illumination direction. Surprisingly, no systematic difference was found between the results for matte and glossy objects. We must, therefore, conclude that there is no evidence from the current study that glossiness influences shape perception although to the observer matte and glossy objects look quite different.