A Discrete Approach for Pairwise Matching of Archaeological Fragments

Abstract

This article addresses the problem of automatic reconstruction of ancient artifacts from archaeological fragments. The technique described here focuses on pairwise matching of flat fragments (typically fresco fragments), and it is intended to be the core of a larger system for artifact reconstruction. Global registration techniques are challenging due to the combinatory explosion that happens in the solution space: the goal is to find the best alignment among all possible ones without an initialization. This fact defines the duality between performance and correction that we face in this work. The proposed technique defines a cost function to evaluate the quality of an alignment based on a discrete sampling of the fragments that ensures data alignment. Starting from an exhaustive search strategy, the technique progressively incorporates new features that lead to a hierarchical search strategy. Convergence and correction of the resulting technique are ensured using an optimistic cost function. Internal search calculations are optimized so the only operations performed are additions, subtractions, and comparisons over aligned data. All heavy geometric operations are carried out by the GPU on a preprocessing stage that only happens once per fragment.