Stochastic Menger using PShape api

NB: This sketch requires the development version of ruby-processing see here.

##########################
# StochasticMenger.rb
# (processing-2.0)
# author Martin Prout
##########################

load_library 'arcball'
import "arcball"

PTS = [-1, 0, 1]
MIN_SIZE = 50
X = 0
Y = 1
Z = 2

attr_reader :arcball, :menger

def setup
  size(640, 480, P3D)
  smooth(8)
  camera
  camera(width/2.0, height/2.0, (height/2.0) / tan(PI*30.0 / 180.0), 0, 0, 0, 0, 1, 0)
  @arcball = ArcBall.new(0, 0, min(width - 20, height - 20) * 0.8)
  @menger = create_shape(GROUP)
  create_menger(0, 0, 0, height * 0.8)
end

def draw
  background(40, 40, 180)
  no_stroke
  lights
  update
  define_lights
  render
end

def render
  menger.set_ambient(50)
  menger.set_specular(150)
  shape(menger)
end

def create_menger(xx, yy, zz, sz)
  u = sz / 3.0
  if (sz < MIN_SIZE) # recursion limited by minimum cube size
    no_stroke
    menger.add_child(create_cube(xx, yy, zz, sz)) # create and add a cube  
  else
    PTS.each do |i|
      PTS.each do |j|
        PTS.each do |k|
          if ((i.abs + j.abs + k.abs) > 1)
            create_menger(xx + (i * u), yy + (j * u), zz + (k * u), u)
          end
        end
      end
    end
  end
end

def create_cube(xx, yy, zz, sz)
  dim = sz / 2.0
  chance = rand
  if chance < 0.8
    cube = create_shape(BOX, sz, sz, sz)
    cube.set_fill(color(0, 0, 219))
  else
    cube = create_shape(SPHERE, dim)
    cube.set_fill(color(224, 223, 219))
  end
  cube.translate(xx, yy, zz)
  return cube
end

def update
  theta, x, y, z = arcball.update
  rotate(theta, x, y, z)
end

def mouse_pressed
  arcball.mouse_pressed(mouse_x, mouse_y)
end

def mouse_dragged
  arcball.mouse_dragged(mouse_x, mouse_y)
end

def define_lights
  ambient_light(50, 50, 50)
  point_light(30, 30, 30, 200, 240, 0)
  directional_light(50, 50, 50, 1, 0, 0)
  spot_light(30, 30, 30, 0, 40, 200, 0, -0.5, -0.5, PI / 2, 2)
end

def key_pressed
  case(key)
  when 'x'
    arcball.select_axis(X)
  when 'y'
    arcball.select_axis(Y)
  when 'z'
    arcball.select_axis(Z)
  end
end

def key_released
  arcball.select_axis(-1)
end