There is an on-line version of the Concave Hull algorithm at: http://local.dsi.uminho.ptThis paper describes an algorithm to compute the envelope of a set of points in a plane, which generates convex or non-convex hulls that represent the area occupied by the given points. The proposed algorithm is based on a k-nearest neighbours approach, where the value of k, the only algorithm parameter, is used to control the “smoothness” of the final solution. The obtained results show that this algorithm is able to deal with arbitrary sets of points, and that the time to compute the polygons increases approximately linearly with the number of points.Fundação para a Ciência e a Tecnologia (FCT) - POSI/CHS/44971/2002
