  The availability of a robust and efficient routine for calculating light
curves of a finite source magnified due to bending its light by the
gravitational field of an intervening binary lens is essential for determining
the characteristics of planets in such microlensing events, as well as for
modelling stellar lens binaries and resolving the brightness profile of the
source star. However, the presence of extended caustics and the fact that the
images of the source star cannot be determined analytically while their number
depends on the source position (relative to the lens system), makes such a task
difficult in general. Combining the advantages of several earlier approaches,
an adaptive contouring algorithm is presented, which only relies on a small
number of simple rules and operations on the adaptive search grid. By using the
parametric representation of critical curves and caustics found by Erdl &
Schneider (1993), seed solutions to the adaptive grid are found, which ensures
that no images or holes are missed.
