Implementation of the Levelset algorithm as originally implemented by Arne-Michael Toersel.
This class provides the getDeltaPhi function to the SparseFieldLevelSet:
deltaPhi = - DELTA_T * image_term * (advection * ADVECTION_FORCE + curvature * CURVATURE_EPSILON)
image_term = 1 / (1 + ((gradients[x][y][z] + greyvalue_penalty) * 2))
advection, curvature from the base functions (upwind scheme and mean curvature)
ADVECTION_FORCE, CURVATURE_EPSILON are weights
This corresponds to the geometric curve evolution proposed by Malladi et.al. (IEEE Trans. on PAMI 16:158)
and Eq. (15) in Caselles et.al. (International Journal of Computer Vision 22:61)
as referenced in the Geodesic Active Contour class of ITK.
The greyvalue_penalty is a modification from Toersel.