Landscape shader in ruby-processing

Feels like I'm on a roll, here is the processing-2.0 landscape shader example running with ruby-processing.

##
# Landscape
# Simple raymarching shader with camera, originally by Paulo Falcão
# Ported from the webGL version in GLSL Sandbox:
# http://glsl.heroku.com/e//3213.0
#
##

attr_reader :landscape, :pg

def setup
  size(640, 360, P2D)

  # This effect can be too demanding on older GPUs, 
  # so we can render it on a smaller res offscreen surface
  # @pg = create_graphics(320, 180, P2D)
  @pg = create_graphics(640, 360, P2D)
  pg.no_stroke()
  @landscape = load_shader("landscape.glsl")
  landscape.set("resolution", width.to_f, height.to_f)
end

def draw
  landscape.set("time", millis() / 1000.0)
  landscape.set("mouse", mouse_x.to_f, height - mouse_y.to_f)

  # This kind of raymarching effects are entirely implemented in the
  # fragment shader, they only need a quad covering the entire view 
  # area so every pixel is pushed through the shader.  
  pg.begin_draw()
  pg.shader(landscape)
  pg.rect(0, 0, width, height)
  pg.end_draw()

  # Scaling up offscreen surface to cover entire screen (if reduced).
  image(pg, 0, 0, width, height)
end