a coffeescript clone of the processing's bouncybubbles example

falling_balls.js.coffee

#
# a coffeescript port of http://processing.org/learning/topics/bouncybubbles.html
#

ids = 0
spring = 0.02
gravity = 0.01
friction = -0.2
force_field = 1.5
balls = []
ground = true

reap_age = 10000

width = 10
height = 800
t = (new Date()).getTime()

p = null

random = (max) ->
  Math.random() * max

class Petri
  constructor: (div) ->
    $(div).html("<canvas></canvas>")
    p = new Processing($('#petri canvas')[0])
    this.setup()
    this.draw()

  run: ->
    setInterval(this.draw, 10)
    setInterval(this.reap, 1000)
    setInterval(this.poll_events, 1000)

  setup: ->
    #d "setup()"
    p.size(width, height)
    p.noStroke()
    p.smooth()

  poll_events: =>
    $this = this
    
    # random events of each type
    $this.add_event({ time: (new Date()).getTime(), type: 0 })
    $this.add_event({ time: (new Date()).getTime(), type: 1 })
    $this.add_event({ time: (new Date()).getTime(), type: 2 })

    # events from a service
    #$.ajax("/events", {
    #  data: { t }
    #  success: (data, textStatus, xhr) ->
    #    for event in data
    #      $this.add_event(event)
    #})

  add_event: (event) ->
    #d "add_event()"
    ids += 1
    i = ids
    #balls.push(new Ball(random(width), random(height), random(40), i, balls, event))
    balls.push(new Ball(5, 0, 10, i, balls, event))
    #d balls[i]

  reap: ->
    #d "reap()"
    #balls = []
    for i in [0...balls.length]
      ball = balls[i]
      if ball.event
        age = t - ball.event.time
      if !ball.event || age > reap_age
        balls.splice(i,1)
      #if (t - balls[i].event.created_at) > 1000
      #  d i
      #  i -= 1

  draw: ->
    #d "draw()"
    p.background(0)
    for i in [0...balls.length]
      balls[i].collide()
      balls[i].move()
      balls[i].display()
    t = (new Date()).getTime()

class Ball

  #            (float, float, float,       int, Ball[])
  constructor: (@x,    @y,    @diameter,   @id, @others, @event) ->
    @color = "#00ff00"
    @vx = 0
    @vy = 0


  collide: ->
    for ball in balls
      dx = ball.x - @x
      dy = ball.y - @y
      distance = Math.sqrt(dx*dx + dy*dy)
      minDist = (ball.diameter/2 + @diameter/2) * force_field
      if (distance < minDist)
        angle = Math.atan2(dy, dx)
        targetX = @x + Math.cos(angle) * minDist
        targetY = @y + Math.sin(angle) * minDist
        ax = (targetX - ball.x) * spring
        ay = (targetY - ball.y) * spring

        @vx -= ax
        @vy -= ay
        ball.vx += ax
        ball.vy += ay


  move: ->
    @vy += gravity
    @x += @vx
    @y += @vy

    if ground
      if (@x + @diameter/2 > width)
        @x = width - @diameter/2
        @vx *= friction
      else if (@x - @diameter/2 < 0)
        @x = @diameter/2
        @vx *= friction

      if (@y + @diameter/2 > height)
        @y = height - @diameter/2
        @vy *= friction
      else if (@y - @diameter/2 < 0)
        @y = @diameter/2
        @vy *= friction

  display: ->
    #d([ @x, @y ])
    #p.fill(255, 204)
    #p.fill(@color)
    max = reap_age - 1000
    age = (t - @event.time)
    age = max if age > max
    alpha = (max - age) / max * 255
    #alpha = 255
    #d alpha
    switch @event.type
      when 0
        p.fill(255,0,0, alpha)
      when 1
        p.fill(0,255,0, alpha)
      when 2
        p.fill(0,0,255, alpha)

    if age >= reap_age
      p.fill(255,255,0)
    #p.fill(255,255,0)

    p.ellipse(@x, @y, @diameter, @diameter)


d = (obj) ->
  console.debug(obj)

$ ->
  petri = new Petri('#petri')
  petri.run()

# vim: ft=coffee