# from ruby opengl samples
# author: gromit <jordan.auge@testic.com>
# roll teh mouse !

require "opengl"
require "glut"

$year = $day = 0

display = Proc.new {
	GL.Clear GL::COLOR_BUFFER_BIT
	GL.Color 1.0, 1.0, 1.0
	
	GL.PushMatrix
	GLUT.WireSphere 1.0, 20, 16	# sun
	GL.Rotate $year, 0.0, 1.0, 0.0
	GL.Translate 2.0, 0.0, 0.0
	GL.Rotate $day, 0.0, 1.0, 0.0
	GLUT.WireSphere 0.2, 10, 8	# planet
	GL.PopMatrix
	GLUT.SwapBuffers
}

reshape = Proc.new { |w, h|
	GL.Viewport 0, 0, w, h
	GL.MatrixMode GL::PROJECTION
	GL.LoadIdentity
	GLU.Perspective 60.0,  w.to_f/h.to_f, 1.0, 20.0
	GL.MatrixMode GL::MODELVIEW
	GL.LoadIdentity
	GLU.LookAt 0.0, 0.0, 5.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0
}

keyboard = Proc.new { |key, x, y|
	case key
	when ?d: $day = ($day + 10) % 360
	when ?D: $day = ($day - 10) % 360
	when ?y: $year = ($year + 5) % 360
	when ?Y: $year = ($year - 5) % 360
	when 27: exit
	else next
	end
	GLUT.PostRedisplay
}

require 'enumerator'
require 'rational'

mousepos = []

motion = Proc.new { |x, y|
	mousepos << [x, y]
	next if mousepos.length <= 10
	mousepos.shift	# eliminate old mousepos

	# calc mean of each consecutive triplet's angle
	angle = mousepos.enum_cons(3).map { |(x1, y1), (x2, y2), (x3, y3)|
		Math::atan2(y3 - y2, x3 - x2) - Math::atan2(y2 - y1, x2 - x1)
	}.inject(0.0) { |a, b|
		a + (b.abs > Math::PI ? 0 : b)
	} / (mousepos.length-2)

	$year += angle * 360 / Math::PI / 5
	GLUT.PostRedisplay
}

GLUT.Init
GLUT.InitDisplayMode GLUT::DOUBLE | GLUT::RGB
GLUT.InitWindowSize 500, 500
GLUT.InitWindowPosition 100, 100
GLUT.CreateWindow $0
GL.ClearColor 0.0, 0.0, 0.0, 0.0
GL.ShadeModel GL::FLAT
GLUT.DisplayFunc display
GLUT.ReshapeFunc reshape
GLUT.MotionFunc motion
GLUT.KeyboardFunc keyboard
GLUT.MainLoop