Showing papers by "Luc Van Gool published in 1992"

Orientational Effects and Component Processes in Symmetry Detection

Abstract: In previous research on symmetry detection, factors contributing to orientational effects (axis and virtual lines connecting symmetrically positioned dots) and component processes (axis selection and pointwise evaluation) have always been confounded. The reason is the restriction to bilateral symmetry (BS), with pointwise correspondences being orthogonal to the axis of symmetry. In our experiments, subjects had to discriminate random dot patterns from symmetries defined by combining 12 axis orientations (every 15°) with seven reflection angles (0°, yielding BS, and three clockwise and counterclockwise 15° steps, yielding skewed symmetry, SS). In Experiment 1, with completely randomized trial order, a significant interaction between axis and skewing angle was obtained, indicating that classically observed orientational effects are restricted to BS and that the orientation of the pointwise correspondences is important. These basic findings were replicated in three subsequent experiments, which differed in t...

Semidifferential invariants: algebraic-differential hybrids

Abstract: In the realm of flexible automation, viewpoint independent object recognition will become increasingly important. An algorithm for the recognition of plane shapes under pseudo- perspective projection is presented. The method is based on the comparison of features that remain invariant under 2-D affine transformations. In particular, the work presented is part of the wider framework of semi-differential invariants. It was successfully tested on a database containing 42 objects.