A new structure of invariant for 3D point sets from a single view

The invariant used as an index has shown many advantages over the pose dependent methods in model-based object recognition. Although perspective and even weak perspective invariants do not exist for general three dimensional point sets from a single view, invariants do exist for structured three dimensional point sets. However, such invariants are not easy to derive. A new special structure for calculating invariants of three dimensional objects is presented. The 3D invariant structure proposed by Rothwell (1993) requires seven points that lie on the vertices of a six-sided polyhedron and is applicable to position free objects. In comparison, the proposed algorithm requires only six points on adjacent (virtual) planes that provides two sets of four coplanar points and does not require the position free condition. Hence it is applicable to a wider class of objects. The algorithm is demonstrated on images of real scenes