3D symmetrical interpretations produced with the 2D curves shown in Figures 9a and 9b individually. The slant of the symmetry plane of the 3D interpretation was set to 40°. Both of the 3D interpretations are composed of symmetrical pairs of non-planar 3D curves. However, the curves in (a) are closer to be planar than those in (b). Note that these 2D curves were generated by distorting a 2D curve in Figure 13 in Sawada, Li and Pizlo (2011, see Demo 4.3 in Sawada, Li & Pizlo, 2011 or Demo 8 in Pizlo, Li, Sawada & Steinman, 2014).