case the displacement is a vector field
are some obvious constraints (see Fig. 4).
1) The shapes of the edges cannot be warped, so
for each edge point.
. Since2) Also, there cannot be any turbulence:
, the displacement field is assumed to be
gradient of some scalar function
.
3) The edge neighborhood points situated farther from the
edge cannot move closer to the edge than the neighborhood
points situated nearer to the edge. This condition can be
described in terms of the constraint (1) where 1D derivative
corresponds to a divergence of 2D vector field