Two dimensional convex hulls:
Animations of Graham's scan can be seen here
here (Princeton). Both these algorithms use angular sorted order
(as proposed in Graham's algorithm), as opposed to the x-sorted
order discussed in class.
Line segment intersection: An animation
of the line sweep algorithm can be seen here
Trapezoidal decomposition and polygon
triangulation: A Java applet for the triangulation of a simple
polygon can be seen here
(University of Bonn, Germany).
This applet illustrates the three-step process of trapezoidal
decomposition, subdivision of the polygon into monotone pieces,
followed by triangulation of the polygon.
Voronoi diagrams: An animation of
Fortune's line sweep algorithm for Voronoi diagrams can be seen here.
This page has links to other Voronoi diagram applets as well (scroll
to the bottom of the page).