Operating instructions:

This applet demonstrates the generation of Glass patterns. The first click of "Graph" generates a
random pattern of dots determined by "Number of Dots". Each subsequent click generates a linear
  transformation of the original pattern with a horizontal magnification "a", vertical magnication "b" and
  rotation angle "Theta". Example: Set "a=0.9", "b=1.1", and "Number of Dots"= 1000, "Theta=0" and hit
 "Graph" two times. Note the saddle (hyperbolic) geometry. Press "Clear" to reset. Now increase the
  value of "Theta" until you see a spiral geometry. Be sure to press "Clear" to reset before trying each
  different value of "Theta". See the Scholarpedia article on "Glass Patterns" for an explanation of the
  eigenvalues and how they reflect the geometry.

Version 2.0 Created by Alex Gorelick & Michael Rozenbojm at McGill University. July 2011