author =       "R. Bar-Yehuda and S. Fogel",
  title =        "Variations on Ray Shooting",
  journal =      "Algorithmica",
  volume =       "11",
  year =         "1994",
  pages =        "133--145",
  abstract =     "We solve some problems related to {\em ray shooting}
    in the plane, such as finding the first object hit
    by a query ray or counting the number of objects
    intersected by the query line. Our main results are
    an algorithm for finding the first hit when the objects
    are lines, and an algorithm for the case when the
    objects are segments. If the segments form simple
    polygons, this information can be used for reducing the
    complexity of the algorithms. The algorithms are
    efficient in space and in query time. Moreover, they
    are simple and therefore of practical use.",