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We describe a model based recognition system, called LEWIS, for the identiication of planar objects based on a projectively invariant representation of shape. The advantages of this shape description include simple model acquisition (direct from images), no need for camera calibration or object pose computation, and the use of index functions. We describe(More)
Projectively invariant shape descriptors efficiently identify instances of object models in images without reference to object pose. These descriptions rely on frame independent representations of planar curves, using plane conies. We show that object pose can be determined from copla-nar curves, given such a frame independent representation. This result is(More)
We present a canonical frame construction for determining pro-jectively invariant indexing functions for non-algebraic smooth plane curves. These invariants are semi-local rather than global, which promotes tolerance to occlusion. Two applications are demonstrated. Firstly, we report preliminary work on building a model based recognition system for planar(More)
A number of recent papers have argued that invariants do not exist for three dimensional point sets in general position 3, 4, 13]. This has often been misinterpreted to mean that invariants cannot be computed for any three dimensional structure. This paper proves by example that although the general statement is true, in-variants do exist for structured(More)
We show how to recover the position and orientation of a pair of known coplanar conics from a single perspective image. We describe and compare a number of methods for determining this relationship. One uses a simple four point back projection model, and the other utilizing transformation invariants. These results can be extended in a number of ways.(More)
In any object recognition system a major and primary task is to associate those image features, within an image of a complex scene, that arise from an individual object. The key idea here is that a geometric class deened in 3D induces relationships in the image which must hold between points on the image outline (the perspective projection of the object).(More)