p5      = processing
img     = null
dirts   = []
coarse  = 16
started = false

class Dirt
  constructor: (img, x, y, nx) ->
    idx = y * img.width + x
    @x  = x + (p5.width - img.width) / 2 + random(coarse)
    @y  = y + random(coarse) + coarse
    @c  = img.pixels.getPixel(idx)
    @a  = 255
    @n  = random(1000.0)
    @w  = random(coarse * 0.5, coarse * 1.5)
    @wd = random(0.9, 0.997)

    @ay =
      0.04 *
      (0.6 - abs(img.width / 2 - x) /
      parseFloat(img.width)) +
      0.03 * noise(nx, @x * 0.02) +
      0.00005 * (255 - brightness(@c))
    @vy = 0
    @ad = 0.95 + 0.05 * pow(@darkness() / 255.0, 2)

  draw: ->
    @vy += @ay
    @px = @x
    @py = @y
    @x += max(0.1, @vy) * (noise(@n, p5.frameCount * 0.1) - 0.5)
    @y += @vy
    @a *= @ad
    @w *= @wd

    strokeWeight @w
    stroke       @c, @a
    line         @px, @py, @x, @y

  alive: -> @y < p5.height and @a > 5 and @wd > 0.05

  darkness: -> 255 - brightness(@c)

preload = images: ["/images/glasses.jpg"]

setup = ->
  size         $(window).width(), $(window).height()
  frameRate    20
  strokeWeight coarse
  noFill()
  img          = loadImage('/images/glasses.jpg')

mousePressed = ->
  if img.pixels.getLength() > 1
    started = true
    background 255

    dirts = []
    nx = random(100.0)

    for y in [0...img.height] by coarse
      for x in [0...img.width] by coarse
        dirts.push new Dirt(img, x, y, nx)
    dirts = _(dirts).sortBy (u) -> [u.darkness]

    image(img, (p5.width - img.width) / 2, coarse)

draw = ->
  if dirts.length == 0 and !started
    mousePressed()

  dirts =
    for d in dirts when d.alive()
      d.draw(); d