empathy.rb

# Empathy
# original by Kyle McDonald
# http://www.openprocessing.org/visuals/?visualID=1182

# This sketch takes advantage of multiple processors by running calculations 
# in a separate thread.

CELL_COUNT      = 5000
SLOW_DOWN       = 0.97
ROTATION        = 0.004
LINE_LENGTH     = 37
MULTI_THREADED  = true

def setup  
  size(500, 500, P3D)
  stroke(0, 0, 0, 25)
  initialize_cells
  start_cell_updates if MULTI_THREADED
end

def initialize_cells
  @cells  = []
  n = CELL_COUNT
  n.times do |i|
    a = i + rand * (Math::PI / 9.0)
    r = ((i / n.to_f) * (width / 2) * (((n - i) / n.to_f) * 3.3)) + (rand * 6)
    @cells[i] = Cell.new((r * Math.cos(a) + width/2).to_i, (r * Math.sin(a) + height/2).to_i)
  end
end

def start_cell_updates
  Thread.new { Kernel.loop { @cells.each {|cell| cell.update } } }
end

def draw
  background 255
  @cells.each {|cell| cell.sense } if started?
end

def started?
  pmouse_x != 0 || pmouse_y != 0
end

def mouse_pressed
  @cells.each {|cell| cell.reset }
end

class Cell
    
  def initialize(x, y)
    @x, @y  = x, y
    @spin   = 0
    @angle  = 0
  end
  
  def reset
    @spin, @angle = 0, 0
  end
  
  def update
    det = ((pmouse_x-@x) * (mouse_y-@y) - (mouse_x-@x) * (pmouse_y-@y)).to_f
    @spin += ROTATION * det / dist(@x, @y, mouse_x, mouse_y).to_f
    @spin *= SLOW_DOWN
    @angle += @spin
  end
  
  def sense
    update unless MULTI_THREADED
    d = LINE_LENGTH * @spin + 0.001
    line(@x, @y, @x + d * Math.cos(@angle), @y + d * Math.sin(@angle))
  end
  
end