Research And Application On Interactive Reassembly Of Fracture Fragments Based On Adjacency Constraint

The computer-assisted artifacts virtual restoration technology is mainly used to solve the problem of the relic reassemble.This technology not only improves the efficiency of manual restoration but also avoids the destruction of cultural relics.The fracture parts of fragments are complicated,the geometric features of some fragments are missing caused by the damage of its fracture parts,it is difficult to use the existing method to merge this fragments.In order to solve this problem,this paper presents a new interactive approach for virtual reassembly of fractured fragments,based on the method of interactive virtual merging,digital geometry and shape matching.Our research has mainly made the following contributions:This paper chooses the geometric texture of the outer surface of the fragments as the feature descriptor,and proposes a virtual reassemble method based on surface adjacency.The geometric structure of models’ surfaces and fracture contours are obtained by generating apparent ridges.In order to obtain matching relation,according to the continuity of geometric structure of models’ surface texture,user can determine the adjacency relationship of the fragments and define the surface adjacency constraints.A region growing strategy is employed to find the correct location of surface adjacency constraint point,then the initial matching points are obtained at the center of this point.After that,the optimal matching points are selected by the line segment constraint.In order to complete the registration of matching models,a shape matching method is proposed to calculate the rigid motion.We present some successful uses of our framework on some fragments of the terracotta warriors,which are Thin-walled fragments with rich geometric texture features.For thicker fractured fragments,the reassembling process is divided into initial alignment steps based on surface adjacency constraints and precise alignment steps based on fracture adjacency constraints.Based on the local geometrical feature of the fracture surface as the feature descriptor,an interactive fragment reassemble method based on the adjacency constraint of fracture is proposed.Firstly,the expert user chooses the fracture surface adjacency constraint point according to the local area of the fracture surface,and forms the fracture surface adjoining constraint cluster,according to adjacent points and the similarity between concavity and convexity of the fracture surface.Then,with the similarity and topological consistency of the adjacency cluster of the fracture surface,the optimal matching cluster is selected by the branching limit algorithm.Finally,the initial alignment result based on the surface adjacency constraint is selected as the initial position,and the improved ICP algorithm is used to realize the precise alignment of the fragments.The method has been applied to the virtual restoration work of the unearthed cultural relics at the K9901 pit of the Terracotta Warriors and Horses,and the experiment has proved that the method has a good effect.