attractor.rb

# http://www.openprocessing.org/visuals/?visualID=2097
s = 500
x0, y0 = 0.0, 0.0

setup do
  alpha_blending true
  background :black
  color :white, 100
end

draw do
  n = 100000
  
  # parameters from http://paulbourke.net/fractals/peterdejong/
  a = 2
  b = -2.53
  c = 1.61
  d = -0.33
  
  # http://nodebox.net/code/index.php/shared_2008-02-29-18-05-38
  translate width/2, height/2
  scale 0.5
  for i in 0..n
    x1 = sin(a*y0) - cos(b*x0)
    y1 = sin(c*x0) - cos(d*y0)
  
    point x1*s, y1*-s
    x0, y0 = x1, y1
  end
end