Shadows in the singular metric
Two examples of shadows (dashed region) of a segment obstacle (green): the
shadows are defined as the sets of positions (x,y) in the plane
reachable from the configuration (0,0,0) of the car by a shortest path
colliding the segment.
for a car-like robot moving forward
J.P. Laumond, C. Nissoux and M. Vendittelli, "Obstacle distances and
visibility for car-like robots moving forward", LAAS-CNRS Report, Dec. 1996.