#
# Copyright (c) 1993-1997, Silicon Graphics, Inc.
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# US Government Users Restricted Rights 
# Use, duplication, or disclosure by the Government is subject to
# restrictions set forth in FAR 52.227.19(c)(2) or subparagraph
# (c)(1)(ii) of the Rights in Technical Data and Computer Software
# clause at DFARS 252.227-7013 and/or in similar or successor
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# Unpublished-- rights reserved under the copyright laws of the
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#
# OpenGL(R) is a registered trademark of Silicon Graphics, Inc.
#
# planet.c
# This program shows how to composite modeling transformations
# to draw translated and rotated models.
# Interaction:  pressing the d and y keys (day and year)
# alters the rotation of the planet around the sun.
require 'opengl'
require 'rational'
include Gl,Glu,Glut

STDOUT.sync = TRUE

$year = 0
$day = 0

def init
	glClearColor(0.0, 0.0, 0.0, 0.0)
	glShadeModel(GL_FLAT)
end

display = Proc.new do
	glClear(GL_COLOR_BUFFER_BIT)
	glColor(1.0, 1.0, 1.0)
	
	glPushMatrix()
	glutWireSphere(1.0, 20, 16)   # draw sun
	glRotate($year, 0.0, 1.0, 0.0)
	glTranslate(2.0, 0.0, 0.0)
	glRotate($day, 0.0, 1.0, 0.0)
	glutWireSphere(0.2, 10, 8)    # draw smaller planet
	glPopMatrix()
	glutSwapBuffers()
end

reshape = Proc.new do |w, h|
	glViewport(0, 0,  w,  h) 
	glMatrixMode(GL_PROJECTION)
	glLoadIdentity()
	gluPerspective(60.0,  w.to_f/h.to_f, 1.0, 20.0)
	glMatrixMode(GL_MODELVIEW)
	glLoadIdentity()
	gluLookAt(0.0, 0.0, 5.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0)
end

keyboard = Proc.new do |key, x, y|
	case (key)
		when ?d
			$day = ($day + 10) % 360
			glutPostRedisplay()
		when ?D
			$day = ($day - 10) % 360
			glutPostRedisplay()
		when ?y
			$year = ($year + 5) % 360
			glutPostRedisplay()
		when ?Y
			$year = ($year - 5) % 360
			glutPostRedisplay()
		when ?\e
			exit(0)
	end
end

glutInit
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB)
glutInitWindowSize(500, 500) 
glutInitWindowPosition(100, 100)
glutCreateWindow($0)
init()
glutDisplayFunc(display) 
glutReshapeFunc(reshape)
glutKeyboardFunc(keyboard)
glutMainLoop()
