spherical_panorama_sample.rb

require 'rubygems'
require "opengl"
require "glut"
require 'RMagick'

module Panorama

WINDOW_WIDTH = 800
WINDOW_HEIGHT = 600

class PanoramaView
  Coordinates = Struct.new(:x, :y)

  def initialize(filename)
    init_glut("Panorama View: #{filename}")
    init_gl
    load_texture(filename)
  
    @viewpos = Coordinates.new(0, 90)
    @viewpos_saved = @viewpos.dup
    @drag_start_pos = Coordinates.new(0, 0)
    @wireframe = false
  end
  
  def run
    run_glut
  end
  
private
  def init_glut(title)
    GLUT.Init
    GLUT.InitDisplayMode(GLUT::DOUBLE | GLUT::RGB)
    GLUT.InitWindowSize(WINDOW_WIDTH, WINDOW_HEIGHT)
    GLUT.CreateWindow(title)
  end

  def init_gl
    GL.Viewport(0, 0, WINDOW_WIDTH, WINDOW_HEIGHT)

    GL.MatrixMode(GL::PROJECTION)
    GL.LoadIdentity
    GLU.Perspective(80.0, WINDOW_WIDTH/WINDOW_HEIGHT, 0.1, 100.0)

    GL.MatrixMode(GL::MODELVIEW)
    GL.LoadIdentity

    GL.Enable(GL::TEXTURE_2D)    
    GL.ClearColor(0.2, 0.2, 0.2, 1.0)

    @qo = GLU.NewQuadric
    GLU.QuadricNormals(@qo, GLU::SMOOTH)
    GLU.QuadricTexture(@qo, GL::TRUE)
  end

  def load_texture_rawdata(filename)
    img = Magick::Image.read(filename.to_s).first
    [img.to_blob { |e| e.format = "RGBA"; e.depth = 8 } + "",
      img.columns,
      img.rows]
  end

  def load_texture(filename)
    raw, width, height = load_texture_rawdata(filename)
    texture = GL.GenTextures(1)
    GL.BindTexture(GL::TEXTURE_2D, texture[0])
    GL.TexImage2D(GL::TEXTURE_2D, 0, 3, width, height, 
          0, GL::RGBA, GL::UNSIGNED_BYTE, raw)
    GL.TexParameteri(GL::TEXTURE_2D, GL::TEXTURE_MIN_FILTER, GL::LINEAR)
    GL.TexParameteri(GL::TEXTURE_2D, GL::TEXTURE_MAG_FILTER, GL::LINEAR) 
    GL.BindTexture(GL::TEXTURE_2D, texture[0])
  end

  def method_to_proc(func)
    self.method(func).to_proc
  end

  def run_glut
    GLUT.DisplayFunc(method_to_proc(:display))
    GLUT.KeyboardFunc(method_to_proc(:keyboard))
    GLUT.MouseFunc(method_to_proc(:mouse))
    GLUT.MotionFunc(method_to_proc(:motion))
    GLUT.MainLoop()
  end
  
  def display
    GL.Clear(GL::COLOR_BUFFER_BIT|GL::DEPTH_BUFFER_BIT)
    GL.PushMatrix
      GL.LoadIdentity
      GL.Rotate(@viewpos.y, 1.0, 0.0, 0.0)
      GL.Rotate(@viewpos.x, 0.0, 0.0, 1.0)
      ds = if @wireframe then GLU::LINE else GLU::FILL end
      GLU.QuadricDrawStyle(@qo, ds)
      GLU.Sphere(@qo, 1.3, 48, 48) # draw sphere
    GL.PopMatrix
    GL.Flush
    GLUT.SwapBuffers
  end
  
  # mouse down/up event
  def mouse(button, state, x, y) 
    if (state == 0)
      @drag_start_pos.x = x 
      @drag_start_pos.y = y
      @viewpos_saved = @viewpos.dup
    end
  end

  # mouse move event
  def motion(x, y) 
    fac = 0.2
    @viewpos.x = @viewpos_saved.x + ((x - @drag_start_pos.x) * fac) % 360
    @viewpos.y = @viewpos_saved.y + ((@drag_start_pos.y - y) * fac) % 360
    GLUT.PostRedisplay() # to redraw
  end

  # keyboard down event
  def keyboard(key , x , y) 
    case (key)
    when ?q
      GLU.DeleteQuadric(@qo)
      exit(1)
    when ?w
      @wireframe = ! @wireframe
      GLUT.PostRedisplay() # to redraw
    end
  end
end

end

if $0 == __FILE__
  panorama = Panorama::PanoramaView.new(ARGV.shift)
  panorama.run
end