Relationship between the Shape and Spacing of Convex Points and the Roughness Sensation in a Dot Pattern Texture

The spacing and curvature of dots are assumed to be factors determining the roughness sensation of a dot pattern. We investigated the relationship between these two parameters and the roughness sensation. We used a three-dimensional printer to produce samples with different combinations of curvature and spacing, and conducted a sensory evaluation to select combinations presenting the same sense of roughness from among them. Experimental results showed that the contour lines of the same sense of roughness are concave and monotone decreasing on the dot curvature versus dot spacing plane. It was found that the roughness sensation is proportional to the logarithm of dot curvature, adopting a previously obtained result that the roughness sensation is proportional to the logarithmic value of the dot spacing. The experiment also revealed non-negligible differences in contour lines among participants and possibility of sorting them into three groups with different roughness perception.