Visual detection of symmetry of 3D shapes

This study tested perception of symmetry of 3D shapes from single 2D images. In Experiment 1, performance in discrimination between symmetric and asymmetric 3D shapes from single 2D line drawings was tested. In Experiment 2, performance in discrimination between different degrees of asymmetry of 3D shapes from single 2D line drawings was tested. The results showed that human performance in the discrimination was reliable. Based on these results, a computational model that performs the discrimination from single 2D images is presented. The model first recovers the 3D shape using a priori constraints: 3D symmetry, maximal 3D compactness, minimum surface area, and maximal planarity of contours. Then the model evaluates the degree of symmetry of the 3D shape. The model provided good fit to the subjects' data.