GLGraphics in ruby-processing post processing (GLSL Fish Eye shader)

# This example applies a post-processing texture filter to the offscreen canvas
# in order to generate an angular fish-eye effect.
# Based on the following discussion thread in the Processing forum:
# http:#forum.processing.org/topic/angular-fisheye
# Some other resources about fish-eye projections:
# 1) Excellent article from Paul Bourke on the math behind the angular fish-eye mapping  
# http:#paulbourke.net/miscellaneous/domefisheye/fisheye/
# 2) Fish-eye effect implemented as a GLSL vertex shader:
# http:#pixelsorcery.wordpress.com/2010/07/13/fisheye-vertex-shader/
# 3) Another fish-eye GLSL shader (didn't test it though):
# http:#pages.cpsc.ucalgary.ca/~brosz/wiki/pmwiki.php/CSharp/08022008

load_libraries 'opengl', 'GLGraphics'
include_package "codeanticode.glgraphics"


attr_reader :canvas, :fisheye, :tex

def setup()
  size(300, 300, GLConstants.GLGRAPHICS)
  # If your video card isn't up to it use following (no antialias)
  #@canvas = GLGraphicsOffScreen.new(self, width, height)    
  @canvas = GLGraphicsOffScreen.new(self, width, height, true, 4)

  # Destination texture to store the fisheye image.
  @tex = GLTexture.new(self)

  @fisheye = GLTextureFilter.new(self, "FishEye.xml")
  # The aperture angle is specified in degrees. Values
  # greater than 180 can be specified, but the result won't
  # be consistent since the mapping is not one-to-one in
  # that case.
  fisheye.set_parameter_value("aperture", 180.0)
end

def draw()
  # Generating offscreen rendering:
  canvas.begin_draw
  canvas.background(0)
  canvas.lights
  canvas.stroke(255, 0, 0)
  (0...height).step(10) {|i| canvas.line(i, 0, i, height)}
  (0...width).step(10) {|j| canvas.line(0, j, width, j)}
  canvas.no_stroke
  canvas.translate(mouse_x, mouse_y, 100)
  canvas.rotate_x(frame_count * 0.01)
  canvas.rotate_y(frame_count * 0.01)
  canvas.box(50)
  canvas.end_draw
  fisheye.apply(canvas.get_texture(), tex)
  image(tex, 0, 0, width, height)
end

This is is an example included with vanilla processing GLGraphics library be sure to copy the shader files from the GLGraphics/Examples/Output/FishEye/data into a data folder (where fish_eye.rb is saved). See also faux fish eye here.