#!/usr/bin/env ruby -rubygems
require 'opengl'
include Gl,Glu,Glut

$light_diffuse = [1.0, 0.0, 0.0, 1.0]
$light_position = [1.0, 1.0, 1.0, 0.0]
$n = [ 
	[-1.0, 0.0, 0.0], [0.0, 1.0, 0.0], [1.0, 0.0, 0.0],
	[0.0, -1.0, 0.0], [0.0, 0.0, 1.0], [0.0, 0.0, -1.0] ]
$faces = [
	[0, 1, 2, 3], [3, 2, 6, 7], [7, 6, 5, 4],
	[4, 5, 1, 0], [5, 6, 2, 1], [7, 4, 0, 3] ]
$v = 0

def drawBox
	for i in (0..5)
		glBegin(GL_QUADS)
		glNormal(*($n[i]))
		glVertex($v[$faces[i][0]])
		glVertex($v[$faces[i][1]])
		glVertex($v[$faces[i][2]])
		glVertex($v[$faces[i][3]])
		glEnd()
	end
end

display = Proc.new do
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
	drawBox
	glutSwapBuffers
end

def myinit
$v = [[-1, -1,1],[-1, -1,-1], [-1,1,-1], [-1,1,1], [1, -1,1],
	[1, -1,-1], [1, 1,-1], [1,1,1]]

	glLight(GL_LIGHT0, GL_DIFFUSE, $light_diffuse)
	glLight(GL_LIGHT0, GL_POSITION, $light_position)
	glEnable(GL_LIGHT0)
	glEnable(GL_LIGHTING)
	
	glEnable(GL_DEPTH_TEST)
	
	glMatrixMode(GL_PROJECTION)
	gluPerspective(40.0, 1.0, 1.0,  10.0)
	glMatrixMode(GL_MODELVIEW)
	gluLookAt(0.0, 0.0, 5.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0)
	
	glTranslate(0.0, 0.0, -1.0)
	glRotate(60, 1.0, 0.0, 0.0)
	glRotate(-20, 0.0, 0.0, 1.0)
end

keyboard = Proc.new do |key, x, y|
	case (key)
		when ?\e
		exit(0);
	end
end

glutInit
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH)
glutInitWindowSize(500, 500)
glutInitWindowPosition(100, 100)
glutCreateWindow("red 3D lighted cube")
glutDisplayFunc(display)
glutKeyboardFunc(keyboard)
myinit
glutMainLoop()