code_brownian_motion.rb

$num = 3000
$range = 12
$ax = Array.new($num, 1280.0/2)
$ay = Array.new($num, 800.0/2)

def app_setup()
  App.background(App.gray(51))
end

def app_update(vg, t)
  # Shift all elements 1 place to the left
  $ax.rotate!
  $ay.rotate!
  $ax[$num-1] = $ax[$num-2]
  $ay[$num-1] = $ay[$num-2]
  # Put a new value at the end of the array
  $ax[$num-1] += Random.rand(-$range..$range)
  $ay[$num-1] += Random.rand(-$range..$range)
  # Constrain all points to the screen
  $ax[$num-1] = $ax[$num-1].clamp(0, 1280)
  $ay[$num-1] = $ay[$num-1].clamp(0, 800)
  # Draw a line connecting the points
  NanoVG.nvgStrokeWidth(vg, 2.0)
  (1...$num).each do |i|
    gray = (i.to_f / $num * 204.0 + 51).to_i
    NanoVG.nvgBeginPath(vg)
    NanoVG.nvgMoveTo(vg, $ax[i - 1], $ay[i - 1])
    NanoVG.nvgLineTo(vg, $ax[i], $ay[i])
    NanoVG.nvgStrokeColor(vg, NanoVG.nvgRGBA(gray, gray, gray, gray))
    NanoVG.nvgStroke(vg)
  end
end

def app_cleanup()
end