R. Malladi et al., SHAPE MODELING WITH FRONT PROPAGATION - A LEVEL SET APPROACH, IEEE transactions on pattern analysis and machine intelligence, 17(2), 1995, pp. 158-175
Shape modeling is an important constituent of computer vision as well
as computer graphics research. Shape models aid the tasks of object re
presentation and recognition. This paper presents a new approach to sh
ape modeling which retains some of the attractive features of existing
methods and overcomes some of their limitations. Our techniques can b
e applied to model arbitrarily complex shapes, which include shapes wi
th significant protrusions, and to situations where no a priori assump
tion about the object's topology is made. A single instance of our mod
el, when presented with an image having more than one object of intere
st, has the ability to split freely to represent each object. This met
hod is based on the ideas developed by Osher and Sethian to model prop
agating solid/liquid interfaces with curvature dependent speeds. The i
nterface (front) is a closed, nonintersecting, hypersurface flowing al
ong its gradient field with constant speed or a speed that depends on
the curvature, It is moved by solving a ''Hamilton-Jacobi'' type equat
ion written for a function in which the interface is a particular leve
l set. A speed term synthesized from the image is used to stop the int
erface in the vicinity-of object boundaries. The resulting equation of
motion is solved by employing entropy-satisfying upwind finite differ
ence schemes. We present a variety of ways of computing evolving front
, including narrow bands, reinitializations, and different stopping cr
iteria. The efficacy of the scheme is demonstrated with numerical expe
riments on some synthesized images and some low contrast medical image
s.