Demo 2. 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).