#
# Copyright (c) 1993-1997, Silicon Graphics, Inc.
# ALL RIGHTS RESERVED
# Permission to use, copy, modify, and distribute this software for
# any purpose and without fee is hereby granted, provided that the above
# copyright notice appear in all copies and that both the copyright notice
# and this permission notice appear in supporting documentation, and that
# the name of Silicon Graphics, Inc. not be used in advertising
# or publicity pertaining to distribution of the software without specific,
# written prior permission.
#
# THE MATERIAL EMBODIED ON THIS SOFTWARE IS PROVIDED TO YOU "AS-IS"
# AND WITHOUT WARRANTY OF ANY KIND, EXPRESS, IMPLIED OR OTHERWISE,
# INCLUDING WITHOUT LIMITATION, ANY WARRANTY OF MERCHANTABILITY OR
# FITNESS FOR A PARTICULAR PURPOSE.  IN NO EVENT SHALL SILICON
# GRAPHICS, INC.  BE LIABLE TO YOU OR ANYONE ELSE FOR ANY DIRECT,
# SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY
# KIND, OR ANY DAMAGES WHATSOEVER, INCLUDING WITHOUT LIMITATION,
# LOSS OF PROFIT, LOSS OF USE, SAVINGS OR REVENUE, OR THE CLAIMS OF
# THIRD PARTIES, WHETHER OR NOT SILICON GRAPHICS, INC.  HAS BEEN
# ADVISED OF THE POSSIBILITY OF SUCH LOSS, HOWEVER CAUSED AND ON
# ANY THEORY OF LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE
# POSSESSION, USE OR PERFORMANCE OF THIS SOFTWARE.
#
# 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
# clauses in the FAR or the DOD or NASA FAR Supplement.
# Unpublished-- rights reserved under the copyright laws of the
# United States.  Contractor/manufacturer is Silicon Graphics,
# Inc., 2011 N.  Shoreline Blvd., Mountain View, CA 94039-7311.
#
# OpenGL(R) is a registered trademark of Silicon Graphics, Inc.
#
# clip.c
# This program demonstrates arbitrary clipping planes.
require 'opengl'
require 'glu'
require 'glut'
require 'mathn'
include Gl,Glu,Glut

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

display = Proc.new do
  eqn = [0.0, 1.0, 0.0, 0.0]
  eqn2 = [1.0, 0.0, 0.0, 0.0]

  glClear(GL_COLOR_BUFFER_BIT)

  glColor(1.0, 1.0, 1.0)
  glPushMatrix()
  glTranslate(0.0, 0.0, -5.0)

  # clip lower half -- y < 0
  glClipPlane(GL_CLIP_PLANE0, eqn)
  glEnable(GL_CLIP_PLANE0)
  # clip left half -- x < 0
  glClipPlane(GL_CLIP_PLANE1, eqn2)
  glEnable(GL_CLIP_PLANE1)

  glRotate(90.0, 1.0, 0.0, 0.0)
  glutWireSphere(1.0, 20, 16)
  glPopMatrix()
  glutSwapBuffers()
end

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

keyboard = Proc.new do |key, x, y|
  case (key)
    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()
