“…Luminance distribution or histogram-based cues are, for instance, the width, average, and skewness of the luminance distribution ( Ho, Landy, & Maloney, 2008 ; Kim & Anderson, 2010 ; Motoyoshi, Nishida, Sharan, & Adelson, 2007 ; Pont & Koenderink, 2005, 2008 ; Wijntjes & Pont, 2010 ). In addition to such relatively easy derivable cues, the spatial properties of 3D textures also provide cues about the illumination, material, and shape ( Chantler, Schmidt, Petrou, & McGunnigle, 2002 ; Gerhard & Maloney, 2010 ; Karlsson, Pont, & Koenderink, 2008 , 2009 ; Kim, Marlow, & Anderson, 2014 ; Knill, 1990 ; Koenderink, 2012 ; Pont & Koenderink, 2008 ; Shepard & Campbell, 1998 ; Varma & Zisserman, 2004 ). The second-order statistics of shaded 3D textures provides us with estimates of the azimuth of the average illumination orientation, that is, the direction modulo 180° ( Koenderink & Pont, 2003 ; Koenderink, van Doorn, Kappers, te Pas, & Pont, 2003 ; Koenderink, van Doorn, & Pont, 2004 , 2007 ).…”