Curves highlight patch boundaries.
Our first algorithm is based on the concept of signed distance. For a point q in , let be the Euclidean distance between q and the closest point on D . An orientable, closed manifold in partitions the space in two regions, an interior and an exterior . We define the signed distance function as the mapping that associates to the point q the distance to the closest point on D , with a positive sign if q lies in the exterior of D , and a negative sign otherwise. We build an initial piecewise-linear approximation of D , so that we can compute for any given q .