SDF fidelity comparisons of our projection methods with previous methods. (a, e, i, m, q, u) Initial LSFs. (b, f, j, n, r, v) Final LSFs. (c, g, k, o, s, w) Initial contours marked by red rectangle and final segmentation results indicated by green contours. (d, h, l, p, t, x) Mean value of penalty energy plots ∫
(|∇ϕ| − 1)2dx (closeness measure between LSF and SDF).