Fig. 2
From: Robust surface normal estimation via greedy sparse regression
Visualization of all observations of one pixel from dataset Caesar. a The pixel studied is marked with blue crosses at the same location (X=90,Y=39) on all images numbered from 1 to 50. b Luminance observations arranged by the image index 1 to 50. c Luminance observations sorted by incident angle. Blue dotted line shows the actual 50 observations; red circled line shows the approximated luminance using least squares; black solid line represents the ground truth matte (Lambertian) luminance