2D Geometry Predicts Perceived Visual Curvature in Context-Free Viewing

Figure 5

Vertically and horizontally oriented ellipses in the two-dimensional plane can be obtained from concentric circles through a geometric transform called planar projection by affinity. In Cartesian space, an ellipse may be defined as the projected image of two concentric circles. In the two examples given here, images of the principal circle and images of the secondary circle generate ellipses through planar projection by affinity with the two circles. In our study, upward oriented and downward oriented arcs of eleven such ellipses, derived from concentric circles with varying diameter, were generated.