Material and shape perception based on two types of intensity gradient information
Fig 4
Probably density distributions of correlation coefficients between all pairs of BRDFs.
(a) The left and right panels show the correlation coefficients on the direction and the magnitude of the intensity gradient of the rendered image, respectively. For the direction condition, the circular correlation was used [29, 30]. Each cell of the panels indicates the correlation coefficient between the BRDFs of rows and columns. The numbers from #1 to #100 indicate the index of MERL BRDFs. (b) The probability density distribution of the correlation coefficients. The top panel indicates the correlation of the direction of the intensity gradient. The bottom panel indicates the correlation of the magnitude of the intensity gradient. When the point light source lit the objects from the viewing direction, the direction of the intensity gradient consistently shows quite a high correlation, whereas the magnitude of the intensity gradient shows correlations that are relatively low and highly variable depending on the comparison pair.